The only difference between Radharani and Krsna, is Krsna IS the Supreme Personality of Godhead and ORIGINAL cause of all causes, and has an extra 4 qualities more than His Visnu-tattva expansions. Therefore, not even Srimati Radharani or Balarama (Krsna's older brother) have all 64 qualities Krsna always has, they have only 60 of those qualities which is 93.75% of Krsna's 64 qualities.

Visnu-tattva expansions of Krsna have 93.75% of Krsna's 100% qualities, this is the correct understanding.

The reason why Krsna has the full 100% is because He has 64 classifications in His personality, 4 of which not even Visnu/Narayana have all the time.

Therefore, the only difference between Radharani (Visnu-"sakti"-tattva), Visnu/Narayana (Visnu-tattva) and Krsna, is Krsna is the Supreme Personality of Godhead and cause of all causes, and has 4 extra qualities than His Visnu-tattva and Visnu-"sakti"-tattva direct expansions have.

Srila Prabhupada - "Tattva is manifested in different ways-

1 - Viṣṇu-tattva, 

2 - Viṣṇu-"śakti"-tattva,

3 - jīva-tattva, like that." (Lecture on SB 6.2.7 - Vrndavana, Sep 10, 1975)

"Sakti-tattva" means the different categories of "energies" of Krsna, the various categories of living entities (Visnu-tattva, Visnu-"sakti"-tattva, Siva-tattva and Jiva-tattva) and non-living sakti (mahat-tattva or matter) as Srila Prabhupada explains. 

Srila Prabhupāda - "Sakti means “energy.” There are many types of energies of the Supreme Lord, and all of them are auspicious." (SB Canto 4 Ch 6 text 43 Purport)

Siva-tattva is neither jiva-tattva, Visnu-tattva or Visnu-"sakti"-tattva. Siva-tattva is in a league of his own having 55 of Krsna's 64 qualities, or having 84.375%

The Visnu-"sakti"-tattva and Visnu-tattva expansions are direct expansions of Krsna, while the jiva-tattva (jiva-souls) are separate expansions of Krsna who have their own personality independent from Krsnas.

The percentage of Krsna's 64 qualities is mathematically worked out here so we can see what His various expansion's are, based on their acquired qualities of Krsna's attributes of 60, 55, and 50-

Visnu/Narayana forms are Visnu-tattva headed by Balarama, while Visnu-"sakti"-tattva Forms are headed by Srimati Radharani.

How much is 60 qualities out of Krsna's 64 as a percentage? Convert fraction (ratio) 60/64

Answer: 93.75%

Siva-tattva - How much is 55 out of 64 as a percentage? 

Convert fraction (ratio) 55/64

Answer: 84.375%

Jiva-tattva (jiva-souls) - How much is 50 out of 64 as a percentage? 

Convert fraction (ratio) 50/64

Answer: 78.125%

Not even Radharani or Balarama have 64 qualities all the time like Krsna does, they have only 60 qualities or 93.75% of Krsna's 64 qualities.

Therefore, all Visnu-tattva or Narayana forms including Balarama, have ONLY 60 qualities or classifications in their personality as explained in Srimad Bhagavatam.

Furthermore, Siva has 84.375% of Krsna's qualities (55 attributes)  and the jiva-tattva's, jiva-souls or marginal living entities like us, have just 78.125% of Krsna's qualities.

There are basically only two types of living entities, Visnu-tattva and jiva-tattva.

Others like Visnu-"sakti"-tattva and also come under the heading of Visnu tattva.

Only Siva-tattva is in a special league of his own with 84.375% qualities (55 attributes) 

As explained, the jiva-tattvas (marginal living entities or jiva-souls) have 78.125% of Krsna's qualities which is having 50 attributes.

Krsna is the ONLY one who has all 64 of His own qualities (100%)

The only difference between Krsna who has 64 qualities, and the Visnu-tattva expansions who have 60 of Krsna's qualities, is those 4 extra qualities Krsna uniquely have.

Not even Balarama or Radharani have 64 qualities all the time like Krsna does, they only have 60 but are still full expansions

Radharani is Visnu-"sakti"-tattva (93.75%)

The only difference between Her and Krsna, is Krsna is the original cause of all causes and has those 4 extra qualities.

So here is what we understand- 

1 - Lord Krsna the Supreme Personality of Godhead and cause of all causes and has 64 qualities or 100%.

2 - Visnu-tattva has 60 qualities = 93.75%.

3 - Siva-tattva has 55 qualities = 84.375%.

4 - Jiva-tattva (jiva-souls) has 50 qualities =78.125%

The Supreme Personality of Godhead Lord Krsna has all these transcendental qualities in full.

Furthermore, the extent of His qualities are inconceivable.

(1) Beautiful features of the entire body

(2) Marked with all auspicious characteristics

(3) Extremely pleasing

(4) Effulgent

(5) Strong

(6) Ever youthful

(7) Wonderful linguist

(8) Truthful

(9) Talks pleasingly

(10) Fluent

(11) Highly learned

(12) Highly intelligent

(13) Genius

(14) Artistic

(15) Extremely clever

(16) Expert

(17) Grateful

(18) Firmly determined

(19) An expert judge of time and circumstances

(20) Sees and speaks on the authority of Vedas, or scriptures

(21) Pure

(22) Self-controlled

(23) Steadfast

(24) Forbearing

(25) Forgiving

(26) Grave

(27) Self-satisfied

(28) Possessing equilibrium

(29) Magnanimous

(30) Religious

(31) Heroic

(32) Compassionate

(33) Respectful

(34) Gentle

(35) Liberal

(36) Shy

(37) The protector of surrendered souls

(38) Happy

(39) The well-wisher of devotees

(40) Controlled by love

(41) all-auspicious

(42) Most powerful

(43) all-famous

(44) Popular

(45) Partial to devotees

(46) Very attractive to all women

(47) all-worshipable

(48) all-opulent

(49) all-honourable

(50) The supreme controller.

Besides all of the above-mentioned fifty qualities, Lord Krsna possesses five more, which are sometimes partially manifested in Lord Brahma or Lord Siva. 

These transcendental qualities are as follows:

(51) Changeless

(52) all-cognizant

(53) Ever fresh

(54) sac-cid-ananda-vigraha (as an eternal blissful spiritual bodily Form)

(55) Possessing all mystic perfections.

Krsna also possesses five other qualities, which are manifest in the body of Narayana/Visnu, and they are listed as follows:

(56) He has inconceivable potency.

(57) Uncountable universes generate from His body.

(58) He is the original source of all incarnations.

(59) He is the giver of salvation to the enemies whom He kills.

(60) He is the attractor of liberated souls.

Besides these sixty transcendental qualities, Krsna has four more, which are not manifested even in the Visnu/Narayana form of Godhead, what to speak of the demigods or living entities. 

They are as follows:

(61) He is the performer of wonderful varieties of pastimes (especially His childhood pastimes).

(62) He is surrounded by devotees endowed with wonderful love of Godhead.

(63) He can attract all living entities all over the universes by playing on His flute.

(64) He has a wonderful excellence of beauty which cannot be rivaled anywhere in the creation.

The Absolute Truth is anandamaya (desiring to increase His joy), hence from His original form He expands and becomes many. These emanations from the Supreme Person are of two categories: full expansions and partially manifested expansions.

The Lord's various full and partial expansions and the Lord Himself simultaneously co-exist, only appearing to manifest under the influence of time.

These expansions of the Supreme Being are known as Visnu-tattva, and they are also Supreme Absolute Truth. While non-different from the Lord, the Visnu-tattvas all accept their own role as Godhead in the mood of Servitor to the "original" Supreme Being.

This relationship is the foundation of Vedic monotheism, which encompasses the inconceivable, absolute personal nature of the original Godhead.

The Supreme Being possesses two other expansive qualities known as Siva-tattva and jiva-tattva. Together with Visnu-tattva, these three qualities are representative of the Absolute Person's internal, external and marginal energies.

The Lord has expanded Himself as Lord Siva and Lord Brahma, and we, the living entities, are also expansions. Like us, Lord Brahma is also jiva-tattva.

Lord Siva is between Visnu-tattva and jiva-tattva. And Lord Visnu is Visnu-tattva. Visnu-tattva, via media, and jiva-tattva - they are all expansions of the Supreme Personality of Godhead.

Therefore we can summarize as

Lord Krsna has 64 qualities or 100%

Visnu-tattva has 60 qualities or 93.75%

Siva-tattva has 55 qualities or 84.375%

Jiva-tattva has 50 qualities or 78.125%

This is the reason why Krsna is called Param Purushottam, Purnavatar or Supreme Personality of Godhead.

Reference from Srimad Bhagavatam Canto 1 Chapter 3 Text 29-

Learned scholars in transcendental subjects have carefully analyzed the summum bonum Krsna to have sixty-four principal attributes.

All the expansions or categories of the Lord possess only some percentages of these attributes. But Sri Krsna is the possessor of the attributes cent percent.

And His personal expansions such as svayam-prakasa, tad-ekatma up to the categories of the avataras who are all visnu-tattva, possess up to ninety-three percent of these transcendental attributes.

Lord Siva, who is neither avatara nor avesa nor in between them, possesses almost eighty-four percent of the attributes.

But the jivas, or the individual living beings in different statuses of life, possess up to the limit of seventy-eight percent of the attributes.

In the conditioned state of material existence, the living being possesses these attributes in very minute quantity, varying in terms of the pious life of the living being.

The most perfect of living beings is Brahma, the supreme administrator of one universe. He possesses seventy-eight percent of the attributes in full.

All other demigods have the same attributes in less quantity, whereas human beings possess the attributes in very minute quantity.

The standard of perfection for a human being is to develop the attributes up to seventy-eight percent in full. The living being can never possess attributes like Siva, Visnu or Lord Krsna.

A living being can become godly by developing the seventy-eight-percent transcendental attributes in fullness, but he can never become a God like Siva, Visnu or Krsna. He can become a Brahma in due course.

The godly living beings who are all residents of the planets in the spiritual sky are eternal associates of God in different spiritual planets called Hari-dhama and Mahesa-dhama.

The abode of Lord Krsna above all spiritual planets is called Krsnaloka or Goloka Vrndavana, and the perfected living being, by developing seventy-eight percent of the above attributes in fullness, can enter the planet of Krsnaloka after leaving the present material body.

Radharani is Sakti-tattva aspect of Visnu-tattva (Visnu-"sakti"-tattva)

Everything comes from Krsna but Krsna needs no one. So in this sense, He is everything and no one exists outside of Him.

Consequently, when Krsna wants to enjoy, He expands the potency or energy within Himself that gives him enjoyment. This potency is a person Krsna expands too. Her name is Srimati Radharani.

She is in a sense also Visnu-"sakti"- tattva because She also is an expansion of Krsna called sakti-tattva. She then is the maintainer of all sakti-tattva internal expansions.

But everything is originally from Krsna.

Radharani is not a different person from Krsna, or, rather, she is both one with and different from Him.

Prabhupada says ultimately there are three types of expansions of living entities.

Visnu-tattva (93.75%), jiva-tattva (78.125%) and then a third category in his own league called Siva-tattva (84.375%)

Only Krsna has 100% of His own qualities, all 64 of them.

Radharani is ALSO Visnu-tattva meaning 93.75% of Krsna's attributes, and so is Balarama also 93.75% (60 of Krsna's 64 attributes)

Krsna has the full 64 qualities and Visnu-tattva has 60.

How could two people be one person or one person be two?

A simple example will illustrate how this is so. The sun cannot exist without the sunshine, nor the sunshine without the sun.

We say, "the sun is in my room"—even though the sun itself is ninety-three million miles away—because the sun appears in the form of its energy.

Therefore the energy (the sunshine) and the energetic (the sun) are simultaneously one and different.

Similarly, Radha and Krsna are simultaneously one and different.

Krsna, the self-effulgent Lord, is the Supreme Personality of Godhead, and Srimati Radharani is His supreme pleasure energy. 

Together They constitute the complete Absolute Truth.

Who can understand all this?

One cannot understand anything about Radha and Krsna through mental speculation.

Krsna and His potencies are achintya, inconceivable, and ananta, unlimited. 

He is the very source of the mind itself, and therefore He is beyond the mind.

The limited mind cannot understand the unlimited Personality of Godhead.

The Vedic literature explains this very logically: "that which is transcendental to material nature is inconceivable, whereas speculative arguments are all mundane.

Since mundane arguments cannot touch transcendental subject matters, one should not try to understand transcendental subjects through mundane arguments.

When ordinary mundane intellectuals try to explain or interpret the identity or pastimes of Radha and Krsna, Krsna's unlimited nature bewilders them, and therefore they misconstrue everything.

Thus they sometimes consider Radha and Krsna to be like an ordinary boy and girl of the material world. But although they often pose as scholars, they do not know what they are talking about.

One should therefore strictly avoid the confused mundane ideas of such blundering intellectuals. 

If one wishes to understand Radha and Krsna, one must understand Them by hearing submissively from a bona fide authority

The original authority on Krsna is Krsna Himself. Everyone is first an authority regarding his own self, and this is also true regarding Krsna.

Moreover, since Krsna is unlimited, no one else can understand Him fully. Krsna's disciple Arjuna confirms this as follows in Bhagavad-Gita As It Is:

svayam evatmanatmanam
vettha tvam purusottama
bhuta-bhavana bhutesa
deva-deva jagat pate

"Indeed, You alone know Yourself by Your own potencies, O origin of all, Lord of all beings, God of gods, O Supreme Person, Lord of the universe!" (Bhagavad Gita As It Is, 10.15)×××