I'm glad you like my headcanons! It's always fun to share my two cents once in a while.
As for Playback!Papyrus... I'm not going to lie, I don't have too much experience with him other than seeing a few pieces of art and short blurbs of his lore so forgive me if I get anything about him wrong.
While I read the comic, a few thoughts I had were the implications of a soulless Papyrus. Can you imagine all of your morals and values becoming the only guidelines on how to do anything? Emotions encompass all forms of feelings like happiness, sadness, grief, anger- And he doesn't feel any of it! He only has memories on how to act in certain situations. "How would I act if I say someone cry?" "How would I act if my brother was upset?" "If I heard a pun, what do I usually do?"
Papyrus would have to try and navigate the would with a whole part of who he is missing!
As for the Flowey aspect, you can probably imagine that before he got a soul, he was empty and all he knew was easter egg knowledge of the world around him. To know secrets and seek more out in the name of curiosity because what else did he have? What do you expect a kid trapped in an immortal body of a flower with the powers to manipulate time an infinite degree and no emotional or moral compass outside of the few years he was alive?
He now has to feel with the crushing guilt of all he's done, all the stunted emotion he hadn't felt in so long. And that might just be enough to make any kid his age turn a new leaf. After all, Asriel was a soft spoken and caring kid before all of this.
