In QFS discourse, soul usually means that part of an individual which is permanent in the sense of surviving physical death and specifically belongs together with that individual and no other. Whether such a thing even exists may depend on the individual itself. For example, an 'organic portal' or 'preadamic man' would not have a soul in this sense, although there would be some sort of non-individuated animating energy in the 'individual soul's' place.
If a soul in this sense exists, it may be more or less evolved. Even if one exists, it may have very little to do with the run of one's life. It may be and usually is for the most part asleep and dissociated from the body's and mind's experience. Using the metaphor of the coach, we could say that the passenger is asleep and the driver/horse take the coach (body) where they please, having quite forgotten about the passenger.
The soul in this sense is linked to the concept of acquiring a real I and gaining access to one's higher centers. These higher centers will exist at least in potential if there is a soul, as we use the word here. At the end of 4th Way evolution, this soul may be substantially identical with the 'real I.' This is however vanishingly rare and various intermediate stages of development are needed before this soul is truly anchored into the body as the conscious master of thought, feeling and physicality.
Much of New Age culture looks for ways for whatever passes for consciousness to deliberately leave the body, experience astral travel, produce psychic effects etc. Quite unlike these, the 4th Way seeks first to bring the soul, if there be any, into the body. The soul needs to first claim its own incarnation from all the forces of personality, biology etc which normally run the show.
Soul is however not completely disconnected and may appear as impulses of conscience, deeper emotions, sense of purpose etc. Man is, even if not run by the 'soul,' still answerable for what transpires through him. In the usual state of matters, the soul gets to karmically pay for the personality's mistakes and predilections even though it is not really in control.