I have both lol, dual ultrawide setup. My main monitor is a 1440p 165hz ultrawide, and i have a 1080p 75hz ultrawide mounted above it that used to be my main monitor before i upgraded. A decent amount of games support ultrawide from my experience, but for some reason mostly japanese games often times don't support it. Usually you can find guides to edit the exe to enable ultrawide support, but i haven't had much luck with that myself. I don't have an oled display or use hdr though, but from my understanding you might be able to make it work in games by using gamescope. For other types of content hdr isn't really there yet, but the good news is that the required wayland protocol recently got merged, so it should be a matter of time before it will eventually be working. I usually always have atleast 2 windows open on my desktop next to each other, and ultrawide is really great for that because it gives each window more width to work with, so you have lots of space.