I never realized that there was a past-lives community!

I think (but am not 100% sure) that agency is the distinction between metempsychosis (souls pick bodies) and reincarnation (souls are assigned to bodies, at random or otherwise)? Certainly at least Plato (in the Republic) and Plotinus (in various places, including this chapter) assume that the souls choose their bodies, while I believe the Buddhists taken reincarnation strictly as a matter of merit.

For my own part, I'm not really sure how it works but tend to trust that it'll all be for the best!