What is Visnu-sakti-tattva?

"Sakti" means the energies of Kṛṣṇa and includes all the different categories of living entities.

The Visnu-"sakti"-tattva category of Krsna's "sakti energy" are actually Viṣṇu-tattva personalities headed by Radharani, the personification of Krsna's internal energy.

Srila Prabhupada - "Tattva is manifested in different ways-

1 - Viṣṇu-tattva,

2 - Viṣṇu-śakti-tattva

3 - jīva-tattva, like that." (SB Canto 6 Ch 2 text 7, Vrndavana, Sep 10, 1975)

The Visnu-"sakti"-tattva and Visnu-tattva Personalities are the eternal inhabitants of Vrindavana and never fall down because they ARE Krsna playing a different role in His own eternal pastimes, they are direct personal expansions of Krsna.

Srila Prabhupada - ''Śrī Kṛṣṇa Caitanya, Śrī Nityānanda, Śrī Advaita, Śrī Gadādhara, and Śrīvāsādi. Śrīvāsādi means jīva-tattva. The jīva-tattva, śakti-tattva, viṣṇu-tattva, these are all tattvas. So Pañca-tattva. Śrī Kṛṣṇa Caitanya is the supreme tattva, Kṛṣṇa. Śrī-kṛṣṇa-caitanya, rādhā-kṛṣṇa nahe anya. We are worshipping Rādhā-Kṛṣṇa. So Śrī Kṛṣṇa Caitanya is Rādhā-Kṛṣṇa combined." (CC Adi-lila 7.5, Mayapur, March 7, 1974)

Srila Prabhupada - "Kṛṣṇa expands Himself into various Viṣṇu-tattva forms, and Śrīmatī Rādhārāṇī expands Herself into various śakti-tattva forms (both expansions are NOT jiva-tattva or jiva-souls), by Her internal potency, as multiforms of the goddess of fortune." (Krsna Book 52)

"Sakti" here refers to Radharani and Her expansions, but also has other meanings too.

Sakti also refers to ALL the energies of Kṛṣṇa, everything is His sakti just like the sunshine is the sun-rays coming from the Sun-disc.

Therefore, sakti-tattva is Visnu-tattva, Visnu-sakti-tattva, jiva-tattva, Siva-tattva and mahat-tattva (the material creation) 

Srila Prabhupada - ''There are Viṣṇu-tattva, jīva-tattva and sakti-tattva. Viṣṇu-tattva is the Supreme Absolute Truth, jīva-tattva is part and parcel, and sakti-tattva is the energy of God." (SB Canto 1 Ch 5 text 15, New Vrindaban, June 19, 1969)

Srila Prabhupada - "Lord is one without a second, and He expands Himself into many for His transcendental pleasure. All the expansions—the Viṣṇu-tattvas, the jīva-tattvas and the śakti-tattvas (the Personalities of Godhead, the living entities and the different potential energies)—are different offshoots from the same one Supreme Lord." (SB Canto 3 Ch 5 text 51 Purport)

The jīva-tattvas (jiva-souls) are separate expansions of Krsna with their own personality separate from Krsna's Personality, while the viṣṇu-tattvas ARE direct expansions of Krsna's Personality.

Even though there are potential differences between them, they are all meant for the transcendental sense gratification of the Supreme Lord.

But sadly, some of the jīva-souls want to lord it over material nature in imitation of the Supreme Personality of Godhead and cause of all causes.

However, as said above, both Visnu-tattva and Visnu-sakti-tattva are NOT jiva-souls, they are Krsna Himself playing a different role in His own pastimes.

In actual fact, the jiva-souls have their independence different from those who are direct personal expansions of Krsna (Visnu-tattva). 

The individual jiva-souls (marginal living entities) are separate "persons" in the Spiritual world, who "choose" to "voluntarily" serve Krsna in an unlimited variety of ways based on their free will.

The constitutional position of the marginal living entities (jiva-souls) are part and parcels of Krsna, voluntarily being His eternal loving servants in their original eternal position.

Srila Prabhupada - "The "immediate" expansions of the Lord are called svāṁśa or "personal direct" expansions (known as Visnu-tattva, where the Lord Himself plays a different role in His own pastimes). The "separated" expansions of the Krsna are called vibhinnāṁśa - (jiva-souls endowed with independence and free will) like us." (BG 10.37, Purport)

The jiva-souls are a spiritual bodily form that "originally" look like Krsna's two-armed bodily form in the spiritual world, and have their own unique personality separate from the Krsna's Personality.

Srila Prabhupada - "The human form is the full manifestation of the jiva-soul." (Melb, May 20, 1975)

Devotee – "Is the original body of the jiva-soul a human form?"

Srila Prabhupada – "Yes, human form. God is also human form. "Man is made after the shape of God." I think there is in the Bible. Is it not? So God is also like human form. Here you see Krsna, two hands, two legs."

Hari-sauri – "How do we understand, then, that there are peacocks and flowers and trees in the spiritual world? Are these not eternal forms?"

Srila Prabhupada – "[describing material form first]: Yes, they are more covered, just like if you cover your body with blanket, the hands and legs are invisible. But you are not the blanket. So the trees and plants, they are more covered. They are not in full manifestation. The human form is the full manifestation of the jiva-soul."

Hari-sauri - "They are covered in the spiritual world?"

Srila Prabhupada - "Not in the spiritual world. There that is voluntary. Some devotees want to serve Krsna as flower; then they become flower there, they lie down at the lotus feet of Krsna as a flower voluntarily, but he can change his form from flower to human body if one wants. That is spiritual life. There is no restriction. If some devotee wants to serve Krsna as cow, he serves Krsna as cow, as calf, as flower, as plant, as water, as ground, field, or as father, as mother, as friend, as beloved, anything. It is inconceivable, yet a fact." (SB Canto 6 Ch 1 text 1-4 - Melb, May 20, 1975)

As said above, the original eternal form of the marginal living entity (jiva-soul) is a "two-arm form" like Krsnas (that the human species also have

Further more, the jiva-souls in Goloka-Vrindavana can choose to enter the Vaikuntha planets where they manifest from their "two-armed form" to a "four armed form" similar to Visnu/Luxmi's bodily forms.^**.