Really I am just bad at tracking things and keeping timelines straight so I worry that with monster I'm more likely to make mistakes and forget which changes happened when.

Witch seems way easier, but potentially less interesting?

If I do go with monster it'll be either vampire or merrow. But right now I'm leaning more toward merrow.

If only because I love the image of merman!Fionn that's in my head. Which is probably a silly reason but whatever.

Also! crescendoll hello! Can I just say I am pretty excited to be throwing Fionn into this mess?

Hey, dude!! I'M SO READY

and I'm all about mermaid fionn too he even has a name pun

consider:

underwater hair aesthetics

I know! His hair would be so pretty underwater. Also I love the idea of him just retreating to the bottom of a lake or river to sulk when he's upset about something.