Ultrawide is completely supported and works with no issues. I've played on two different monitors with ZERO issues. No special launch codes necessary either.
With that being said, I would not recommend UW for FPS games. First game I loaded up when I got mine was BF2042, and it was very impressive looking. However, it was a bit overwhelming because there was more I could see in my peripheral vision. I found it not very useful to see more, if anything, it was more distracting, and UI elements were further away. Even when I loaded up a couple of MMO's, I didn't find myself enjoying the game more like I thought that I would.
If you do anything that requires two monitors, then UW is the way to go in my opinion. If you're mostly gaming, then the standard 27 inch, 16:9, monitor is 100% the right size for me. Everyone is different, but after trying both, standard is the best for gaming. Also, you can usually set your UW monitor to 16:9 in game, and will act like a regular monitor. That's how I ended up using my UW for Apex.
If you're getting 144 on 4k and not getting crazy FPS drops, your monitor won't be whats holding you back.
My recommendation would be 1440p, 175 or higher, 27 inch, OLED. Moving to a 1440 was a pretty big upgrade, in Battlefield I could see outlines of soldiers better. After 175 refresh rate, I can barely tell the difference, but that's on OLED, which is supposed to have the equivalent blur rating of 1.5 of an IPS monitor, so 180 on OLED feels like 240 for example. If you're on IPS, then 240 is the move.
There's some cool new monitors that do both 4k and 1080, 144 for the 4k, and then like 360 for the 1080 I think, but I'm not personally satisfied gaming on 1080 anymore.
Hope that helps, feel free to ask questions. I've owned both UW and regular monitors, both in IPS and OLED, so a decent amount of experience. I mostly play BF and Apex atm as well.