Technically,
The Innermost Feelings are a "final stage" but the game doesn't end there because the Subconscious is something that needs to be discovered. And going from the Subconscious to the Limen is another thing of its own. So I guess that counts as a post-game?
The epilogue will be dependent on the ending you get, but in general it'll be the full reveal of how the person has been undergoing severe stress and facing many personal demons. I do want one of the good endings to have a "explore a healed mind" mode, but that's for much later down the line haha.
If Innermost Feelings has no actual ending, and you still need to unlock the Subconcious stage, it's not really post game. Unless of course Innermost Feelings is supposed to be a "Disc One Final Dungeon" which is fine.
Would there also be a joke ending or any alternate endings or will it just be the Good and Bad Endings?