Fairies don't have wings, they just levitate.
Angels are terrifying creations created to guard the floating isles, they're like 'machines' with no real mind or intelligence.
Demons are just shapeshifter that takes on whatever form they'd like, to a limit. Originally taking on forms amalgam of beasts to easily outplay their prey. Then human forms to prey upon them through deception and wit, with no 'humanity' on their mind. But as time goes on, they started to enjoys living human lives and some started prefer living in human societies in disguise over their own.
Other demons can't deny they prefer a humanoid form to utilise tools or the intelligence they've gain to build their own societies and enjoy life in different ways than before. The way I worldbuilt it, demons started off as mindless beasts, but eventually gained the ability to empathise and arguably became humans in most aspects, except for their mortality.
I like the idea of 'angels' to be terrifying things, and 'demons' to be as beautiful as they'd like to be. Though of course most human don't enjoy the idea having demons in their cities and towns living normal lives, they'll never be inherently 'beautiful' in that mannerism. Subjective.