I'm using a Samsung C49RG90. I have to say that this monitor has made choosing a Mac a difficult task.
The monitor is 5120x1440 but my old MBP 2015 would only run it at 3840x1080 across HDMI (and not at all across TB/DP). I wanted a Mac Mini (Intel) and that has problems with 5k2k screens, so I cancelled that order and got a MBP 2019 16", and that worked at 5120x1440 but the fans came on immediately. See the "
16" is HOT & NOISY with an external monitor! " thread, with literally 4700+ replies. So I sent the MBP 16" back.
Got a Mac Pro with Radeon 580X, which works really well at 5120, but discovered after a few days that I really couldn't focus on the small type at the far ends of the screen, so moved to 3840, but suffered from terrible flickering and swim (across both HDMI and USB-C/DP). Moving back to the MBP2015 was a relief. Eventually fixed the Mac Pro + 580X flicker/swim problem with SwitchResX, using the 59.88Hz option (99.88Hz works too).
Ordered an M1 Air 16GB, and to cut a long story short, could only get 3008x846 or some such similar, totally nuts resolution. Sent the M1 Air back.
All that said, I'm quite attached to having the space to view three documents side-by-side, or a document and some other windows like messaging/file management. Much nicer than two 'normal' sized displays, even if the total coverage is the same.