@FallenreaperTheir appearance is largely set apart from their abilities, but a fire user with gills wouldn't make much sense, xD.
As for your Firebug. She could likely singe her blanket when she was a little kid. This RP leaves her at fifteen years of age, up to eighteen, where her powers will have matured enough to be more 'house consuming.'
In this world, a mutant's powers are more natural to them than in the X-Men, because they manifest at a much younger, single-digit age, and just develop from there.
At twelve years old, the powers will have grown enough to require surveillance so no one gets hurt.
I hope that makes sense.
__________________________________________
@RedVIIDon't stress it, you have time.
__________________________________________
Tomorrow I'll get a Discord up, for now, I have to head to bed. I'll see y'all in the morning.