The jiva-souls are NOT formless, nor do they originate from an impersonal source within the brahmajyoti, no, the jiva-souls are eternally a "spiritual bodily form" in their original and eternal position and potential.

Srila Prabhupada - "The spirit soul is NOT formless; it has got form, the spirit soul always has form and is expressed as hands, legs, heads, everything. But with our material eyes at the present, our gross eyes, we cannot see these facts; therefore we foolishly believe the jiva-souls have no form." (Lecture on BG, Ch 2 Text 14, Mexico, Feb 14, 1975)

From that original form of the jiva-soul all other forms are voluntary and possible, such as the 4 armed form on the Vaikuntha planets similar to Lord Visnu's Body. The jiva-souls first fall from Goloka-Vrindavana and the Vaikuntha planets.

So, being an inactive (dormant) "spark in the brahmajyoti," is a conditional state the jiva-souls fall too AFTER becoming fed up with material existence and its troublesome cycle of repeated birth and death.

One's original feature and full potential as a person is a bodily form like Krsnas. Man in this material world is made in the image of Krsna in Goloka-Vrindavana, therefore, all jiva-souls are eternally a spiritual bodily form. 

Only when the jiva-souls continue to fall do they eventually appear as a formless or impersonal "spark" or bodiless individual unit in Krsna's effulgence (the impersonal brahmajyoti)

Krsna is behind everything. He is both "all-pervasive impersonally" and an individual PERSON as an eternal bodily form. 

Ultimately, we are individual PERSONS as an eternal bodily form in our full potential in the spiritual world. This is our original and eternal position, and not some bodiless dormant spark in the impersonal brahman or brahmajyoti.

Originally and eternally our bodily appearance is similar to Krsna's form, but we can voluntarily change that at ant time and be a flower, or a tree, or gopi, or cowherd boy, a chair Krsna sits on, or the grass Krsna walks on, or a cloud in the sky Krsna admires, the choices are unlimited.

You can be the flag pole on Krsna's chariot, or even Krsna's chariot, and at any moment change back to a 2 armed or 4 armed human like form. No bodily form is fixed in the Spiritual worlds, your rasa can constantly change.

It is all voluntary, you can be what ever you want to be serving Krsna or Visnu/Narayana  if it is you genuine desire to please or amuse Krsna.

Devotee - "What is the form of the spiritual body. If the spirit soul is non-material, what is the form?"

Srila Prabhupāda - "There is form, just like this material body is compared with the dress. Now, just like in your present material form you have got hand; therefore your coat has got hand. You have got legs; therefore your pant has got legs. Therefore it is to be assumed that the spirit soul always has got form, and is expressed as hands, legs, heads, everything. The spirit soul is not formless; it has got form. But with our material eyes at the present, gross eyes, we cannot find it; therefore we say and foolishly believe it has no form." (Lecture BG, Ch 2 Text 14, Mexico, Feb 14, 1975)

The full potential and original feature of ALL marginal living entities (jiva-souls) is a two-arm form like Krsna's Body.

Devotee – "Is the original body of the spirit 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 dasa – "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 soul."

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

Srila Prabhupada - "Not in the spiritual world. There that is voluntary. Some devotee wants to serve Krsna as flower; they become flower there. If I want to be a flower I shall lie down at the lotus feet of Krsna, he becomes flower, voluntarily, and he can change his, from flower to human body. 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)

In the spiritual world the choice of the jiva-soul's relationship with Krsna is always voluntary, from a blade of grass to a tree, a cow or gopi or a 4 armed form on the Vaikuntha planets serving Narayana (Visnu).

Srila Prabhupada - "Your question about one's relationship with Lord Krsna on Krsnaloka, does he ever fall down? The jiva-souls are endowed with minute independence as part of their nature and this minute independence may be utilized rightly or wrongly at anytime, so there is always a chance of falling down by misuse of one’s independence." (Letter to Jagadisa dasa, 4/25/1970)

Srila Prabhupada - "In the broader sense, everyone comes from Krsnaloka (Goloka-Vrindavana). When one forgets Krsna, he is conditioned (nitya-baddha), when one remembers Krsna he is liberated (nitya-siddha)." (Letter to Mukunda, June 10, 1969)

Srila Prabhupada - "The "immediate" expansions of the Lord are called svāṁśa or personal direct expansions (Visnu-tattva who are Krsna playing another role in His own pastimes) The "separated" expansions of the Lord are called vibhinnāṁśa - (jiva-tattva) or independent jiva-souls like us." (From BG, Ch 10 Text 37, Purport)

The jiva-souls do not originate from the Impersonal Brahman or the Body of Maha-Visnu or tatastha-sakti as some believe. All the above are already a fallen condition of the jiva-souls that they have fallen too. The jiva-souls are eternal and have always existed without beginning or end.

As Bhagavad Gita As It Is correct 1983 edition Chapter 2 text 20 reveals-

Bhagavad Gita As It Is - "For the soul there is neither birth nor death at any time. He has not come into being, does not come into being, and will not come into being. He is unborn, eternal, ever-existing and primeval. He is not slain when the body is slain." (BG Ch 2 text 20)

As said above, the jiva-souls who enter the impersonal brahmajyoti, the Body of Maha-Visnu and tatastha-sakti in a dormant state, have fallen to that condition Srila Prabhupada explains here-

Srila Prabhupada - "Existence in the impersonal brahman is also within the category of non-Krsna consciousness. Those who are in the brahman effulgence are also in the fallen condition, so there is no question of falling down from a fallen condition. When fall takes place, it means falling down from the non-fallen condition. The non-fallen condition is Krsna consciousness." (Letter to Revatinandana, Los Angeles 13 June, 1970)..*^*..