Nilfgaard under Ciri would be good for the Elves. And the most I saw of Emhyr treating the Elves was him barely giving a shit, which is an upgrade from the North setting them on fire or treating them like shit.
Well, the elves have been well... the Socia'tael aren't exactly nice people, and incredibly persistent when it comes to desiring violence as a means to an end. The Socia'tael are technically open to all non-humans but the halflings, gnomes, and dwarves have generally accepted their circumstances and done their best to assimilate, and as a result have the fewest problems and thus desire to chimp out that the elves do for some odd reason.
Which is really fucking hilarious because not long after the humans showed up and started causing problems the older and wiser of the elves went "Holy shit, we don't have the numbers and never will have the numbers to contest them due to reproductive differences", but one young genius who thought he knew better decided to rally every young, able-bodied, and fertile elf he could and challenged the humans to a single, epic, decisive battle. The battle itself was a bloodbath that resulted in no immediate victory for either side but long-term it resulted in the elves getting demographically fucked even worse, much like how Russia never really managed to unfuck itself after WW2, or France after the Napoleonic Wars. Their problems are all entirely of their own making, so I don't really have any sympathy for them.
EDIT: I'd like to point out that the Witcher books are an inversion of the usual fantasy trope of "woe is us, our heroes and legends are long past, and it sucks ass because things are shit now". Things are not shit for mankind, but the best they've been to the point that until we started killing each other
en masse the monsters had been controlled and contained to the point a large portion of Geralt's poverty was just a lack of work monster slaying. Whenever a forktail would pick off a farmer's sheep the lord would just pay the dude off since it was cheaper and easier than sending guys out into the hills to kill it, and besides, his daughter thought that forktail was pretty. Trolls are left alone because their bridge tolls are cheaper than what lords ask, and they keep their houses in better condition than a lord keeps his bridges in.
Hell, towards the end of the books a dwarf laughs at the humans chasing after every centuries-old elven relic blade (actually made by the dwarves naturally, the elves just making the fancy bits like the handguard) and just hands him his own sword, fresh from the Mahakam forges, and boasts to Geralt of the greatness of modern technology. Said blade, when backed by a witcher's enhanced strengh, slices clean through chain mail like it wasn't there.
So yeah, we're on top, the fucking
kings, and the non-humans either need to adapt and learn (like the dwarves, who wind up running the banks in Novigrad, a city dominated by the infamously anti-nonhuman Church of the Eternal Fire), or just be a bunch of treeniggers like the elves and eventually go extinct. That said there are plenty of various city elves, and while Geralt thinks they're weird because they dress in a mishmash of human and elven styles and drink herbal tea instead of booze, they're largely tolerated by the humans
because they don't cause trouble.
