Dear soul,
Thank you for your question.
I don’t know the exact answer. Gyan does not go too much into that “realm.” I can only speculate.
It is believed that the “subtle body” will be the way to “settle our karmic accounts” through “Dharamraj” before going into the soul world. Therefore, that is the “only” subtle body that we know in Gyan.

Also, we are aware of the existence of ghosts, astral bodies and such; which could appear at any other time in our rebirths from the copper age onwards, which many may call “subtle bodies” as well.

As far as the “advanced party” deal; there is no much information about them; so I can “logically” speculate that once you go into the “advanced party,” you will not be a BK again. Effort making is over at that point for their Dharna will allow them to progress through other means/experiences.

They no longer need the “reformation of the self” of BK life. Their “role” is to be the “bridge” between the “ways and knowledge” of the old world and the “ways to be and live” of the Golden age.

In the Drama everything changes little by little; thus, before a “Golden age” society, there is a need for something similar to them which will bring technology and know-how for a different society. That is their main role.

Best wishes!