I will say this, wholly my own opinion:
I was a curmudgeon about this. I thought ultra-wide was a gimmick, that "immersiveness" was just a buzz-word used to sell it, and that curved screens even more of a gimmick.
I will still stand by the thought that curved screens, in standard 16:9 widescreen, are a gimmick.
Ultra-wide, though, I've gone from a skeptic to a true believer. And, once you get to the 34-inch level of ultra-wide, a curve helps.
The extra field-of-view, even in non-first-person games, is something you don't think you want or need until you have it. Then you wonder how you lived without it. For me, this enhances the enjoyment of games.
My own monitor is 3840x1600, FreeSync 48-75 Hz, 38-inch. I really wanted that much horizontal space for work purposes, to emulate the dual 1920x1080 monitors that I have in the office. That said, I probably could've lived quite easily with 3440x1440, which would've been akin to dual 1720 width, and then gaming would be a bit easier on the video card. For work, in hindsight, I could've easily lived with a 10% loss of horizontal resolution.
My son's is a 2560x1080, and it has a FreeSync range of 50-144, 34-inch, though LFC effectively makes it 25-144. His video card can't really manage high refresh rates, and my son likes the details turned up. The adaptive refresh that FreeSync gives, though, keeps things smooth.
Some would suggest that 2560x1080 is too low of a resolution for a 34-inch screen. I'd disagree, but my eyesight's not the best. My son, however, having very sharp vision and being young, concurs with me. Plus, if you ever decide to go for a faster refresh rate, it will take a less expensive video card to do that at 2560x1080 than it would on the standard 16:9 resolution of 2560x1440, not to mention any higher resolutions.
That all said, everyone's eyes are different. What I might think looks great, you might agree with, or you might disagree with. Both of the monitors I mentioned were reviewed at Tom's Hardware, and that was part of the motivation to get the particular models that I did. Despite that, before getting the first one (the 38" Acer), I did go to a local MicroCenter to see what ultra-wide felt like, having two windows on the desktop side-by side, etc. though I did not get to game. They didn't have the specific monitor I wanted on display, but seeing other large (34-35 inch) monitors and trying them out convinced me. They did have my monitor in stock, though, so I drove home with it that day.
If it is at all possible, see it in person, whether at a store, or a friend who owns one, etc. Your eyes are the best judge, though reviews are certainly helpful.