I do enjoy thinking about the differences between "I remember my past life, but the past is not me; that's someone else entirely" and "I remember my past life, but I'm still partly the same person as I was before (mixing of the souls)" and "I remember my past life/the other world, and that makes me completely different from who I was before" and "I have memories from both worlds, but I am NOT the original person, even if I have their memories" and "I have no memories of this new world but must live as the original, regardless." Each version has it's own interesting perspective whether memories affect identity, even as one changes from having them or not. So many isekai stories strictly differentiate between "the original goods" and the "transmigrator/reincarnator" but I think, in reality, the truth would be much more murkier and difficult to deal with.
