This is all super useful, thank you!
are they sort of nocturnal, or do they just have a LOT of coffee to keep awake 24/7?
They're awake pretty much 24/7 via magic, but the magic is pretty taxing and they do have to sleep once every month or so. When they do so, they have to be supervised and protected by a mage who knows what they're doing, lest they fall prey to any sneaky demons.
what makes their economy so bountiful?
Modern human society in my story is pretty centered around trade. The first human-run city on the continent shared by elves and humans was a coastal trade hub, and in general the leadership of their kingdom has placed value on versatility of goods. The main reason they've been so prosperous, though, is that their only real competitors in terms of having high quality goods are the elves, and the elves don't like trading much. They give gifts, but they do not sell, and they like to be self-sustaining in their settlements. (Dark elves, that is.) It's mainly a cultural thing.
I'd suggest something maybe to do with animal domestication or warfare, unless you already have ideas.
They're much better at warfare. Much much much better. Elves are squishy little things, even the most hardened, and typically stick to poisonous arrows and control over their environment (through both setting traps and literally controlling their environment with all their weird magic). While elves get weighed down by armour and are useless with swords, humans (those of the kingdom in my story, that is) are known for their craftsmanship, and have a much higher capacity for muscle mass. My elves aren't pacifists, they're just not built for warfare. They're arguably more violent than the humans are despite that.
Animal relations are more of a wood elf thing. They don't domesticate, but to varying degrees elves have a sort of mycelium like connection with their land, and are able to almost tap into the intuitions of animals. Dark elves can do it too, but their magic relies a lot more on demons and enthralling the unsuspecting than anything inherent in natural life.