@cleoone thing I really like tbh is the buttons in the top on mobile and the star button (though I personally think if we're gonna have a star button it should be its own thing and we should be able to have multi reacts like we do on Akkoma/Pleroma; this is also why I dislike star -> Favorite as that's already how Misskey backwards-compatibilizes its reactions and doing that just causes weird issues when liking on older misskey instances (⭐️-> 👍))
this is all personal preference, but like for example scrolling profile images that follow your screen are missing from calckey
i also don't prefer the icon set that calckey uses, or the floating create note button
there's a few other things I change on my instance too, like removing gaps in posts and disabling all blur effects.
But tbh that's the great thing about running my own instance and FOSS software, is that I'm not precluded to anyone's work I like. I'm able to choose what I think is great and use that for myself while others have the same choice