Kāraṇārṇavaśāyī Viṣṇu, (Maha-Visnu) is an expansion of Balarama, both Garbhodakashayi Visnu (Hiraņyagarbha) and Ksirodakaśāyī Visnu (Paramatma or Supersoul) are also expansions of Mahā-Visnu.

Kāraṇārṇavaśāyī Viṣṇu, is the plenary part of the original Personality of Godhead, Śrī Kṛṣṇa, described in the Brahma-saṁhitā (5.48) as follows-

"All the innumerable universes are maintained only during the breathing period of Mahā-Viṣṇu, or Kāraṇārṇavaśāyī Viṣṇu, who is only a plenary part of Govinda, the original Personality of Godhead Lord Kṛṣṇa."

Garbhodakaśāyī Visnu is an expansion of Kāraṇārṇavaśāyī Viṣṇu (Maha-Visnu), who is an expansion of Narayana/Visnu on all the Vaikuntha planets. 

All Visnu expansions come from Balarama, and Balarama is Kṛṣṇa's first expansion.

In Vrindavana pastimes, Balarama is the older brother of Krsna. However, it is Krsna who is the Supreme Personality of Godhead and cause of all causes.

Srila Prabhupada - "In Gaudīya Vaisnavism, the "Sātvata-tantra" describes three different forms of Visnu as- 

"For material creation, Lord Krsna's plenary expansion assumes three Visnus- 

The first one, Kāraṇārṇavaśāyī Viṣṇu, (Maha-Visnu), creates the total material energy, known as mahat-tattva. 

The second, Garbhodakasayi Visnu, (Hiraņyagarbha) enters into all the universes to create diversities in each of them. 

The third, Ksirodakasayi Visnu, is diffused as the all-pervading Supersoul in all the universes and is known as Paramatma, who is present even within the atoms. 

Anyone who knows these three Visnus can be liberated from material entanglement." (BG, As It Is  Ch 7 text 4) 

The role of the three Viṣṇus is further explained as follows-

1 - Kāraṇārṇavaśāyī Viṣṇu, (Mahā-visnu), 

2 - Garbhodakaśāyī Visnu (Hiraņyagarbha) 

3 - Ksirodakaśāyī Visnu (Paramātmā or Supersoul)

Each form has a different role in the maintenance of the material universe including its inhabitants.

For the material creation, Krsna's plenary expansion assumes three Visnus. 

1 - The first, Mahā-Viṣṇu, creates the total material energy, known as the mahat-tattva where all the Brahmanda universes are spread throughout the material creation.

2 - The second, Garbhodakaśāyī Viṣṇu, enters deep inside each Brahmanda universe and creates a secondary universe.

3 - The third, Kṣīrodakaśāyī Visnu, is diffused as the all-pervading super-soul in all the universes inside each Brahmanda, and is in the heart of every living being. Kṣīrodakaśāyī Visnu is also known as Paramātmā. He is present even within the atoms.

The goal of life is to know Kṛṣṇa, who is situated within the heart of every living being as Paramātmā, the four-handed Viṣṇu form.

This material world is a temporary manifestation of one of the energies of the Lord. All the activities of the material world are directed by these three Visnu expansions of Lord Krsna. 

These Purusas are called incarnations. Generally one who does not know the science of God (Krsna) assumes that this material world is for the enjoyment of the living entities and that the living entities are the causes (Purusas), controllers and enjoyers of the material energy. 

According to Bhagavad Gita As It Is this atheistic conclusion is false. 

In the verse under discussion it is stated that Krsna is the original cause of the material manifestation. Srimad Bhagavatam also confirms this. 

The ingredients of the material manifestation are separated energies of the Lord. 

Even the brahmajyoti, which is the ultimate goal of the impersonalists, is a spiritual energy manifested in the spiritual sky. 

There are no spiritual diversities in brahmajyoti as there are in the Vaikunthalokas, and the impersonalist accepts this brahmajyoti as the ultimate eternal goal.

The Paramatma (Supersoul) manifestation is also a temporary all-pervasive aspect of the Ksirodakasayi Visnu. 

The Paramatma manifestation is not eternal in the spiritual world. Therefore the factual Absolute Truth is the Supreme Personality of Godhead Krsna. He is the complete energetic person, and He possesses different separated and internal energies.

In the material energy, the principal manifestations are eight, out of these, the first five manifestations, namely earth, water, fire, air and sky, are called the five gigantic creations or the gross creations, within which the five sense objects are included. 

They are the manifestations of physical-

sound, 

touch, 

form, 

taste,

smell. 

Material science comprises these ten items and nothing more. But the other three items, namely 

mind, 

intelligence,

false ego.

All are neglected by the materialists. 

Philosophers who deal with mental activities are also not perfect in knowledge because they do not know the ultimate source, Krsna. 

The false ego-"I am," and "It is mine," which constitute the basic principle of material existence-includes ten sense organs for material activities.

Intelligence refers to the total material creation called the mahat-tattva. 

Therefore, from the eight separated energies of the Lord are manifest the twenty-four elements of the material world, which are the subject matter of sankhya atheistic philosophy; they are originally offshoots from Krsna's energies and are separated from Him, but atheistic sankhya philosophers with a poor fund of knowledge do not know Krsna as the cause of all causes. 

The subject matter for discussion in the sankhya philosophy is only the manifestation of the external energy of Krsna, as it is describe in the Bhagavad Gita As It Is.

Kāraṇārṇavaśāyī Viṣṇu, is the first incarnation of the Supreme Lord, and He is the master of eternal time, space, cause and effects, mind, the elements, the material ego, the modes of nature, the senses, the universal form of the Lord, Garbhodakaśāyī Viṣṇu, and the sum total of all living beings, both moving and non-moving.

Garbhodhakaśāyī Visnu is an expansion or overload of Maha-visnu (expansion of Saṃkarṣaṇa of second caturvyūha, which is an expansion of Narayana from Vaikuntha, who is an expansion ultimately of Balarama in Goloka-Vrindavana, Krsna's first expansion. 

Garbhodhakaśāyī Visnu is realized as the form of Pradyumna within the material universe. He is the father of Brahmā who appeared from His navel and hence Garbhodakashayi Visnu is also called Hiraņyagarbha.

Why is there no Paramatma (Supersoul) on the Vaikuntha planets, or Goloka Vrindavana?

Paramatma or Supersoul manifests as Krsna in Goloka-Vrindavana or as Visnu on the Vaikuntha planets in the Spiritual world. 

The Paramatma (Supersoul) form of the Lord only accompanies the "fallen jiva-souls" while they roam in the material world confined to a temporary material bodily vessels experiencing the repeated birth and death of those bodies.

Krsna is always with the individual jiva-souls however, in the material world manifests as the 4 armed Paramatma form in the heart. 

When the jiva-souls (marginal living entities) qualify to again return back home back to Godhead, or re-enter the spiritual world after being fallen in the material world, the Paramatma form (Supersoul) of the Lord becomes directly Krsna or Visnu, depending on one's voluntary relationship with the Lord in His pastimes.^*^.