I totally agree with the latest comment by @WingWarper1.
27in / 1440p is a sweet spot - it’s bigger than a regular work-type monitor, and the resolution gives you better visuals. 4K would look slightly better at 27in, but much less so than on a larger screen.
Ultrawide or curved options are really down to your preferences, and what will fit in the space available. My 32in 4K monitor has to be on the desk as I use it for work also, and given the little corner my office is in I couldn’t have gone very much larger even, if it was on the wall.
One thing that makes a big improvement in immersion for me is the use of a Tobii 5 head / eye tracker. Without the need to wear a hat or headset, you get 180 degrees panoramic vision from a single flat monitor. This brings it much closer to the effects you get from a multi-screen setup or a VR headset, but without the bulk, cost, complexity and considerable further downsides of those approaches.
Again as WW1 mentioned, if you can find a 4K tv that maxes out the space available then go for it, but do check it has some suitable gaming features too. Most modern ones have at least a few in order to accommodate consoles & other external devices.
Useful things are: Low input lag, high refresh rate (although this isn’t essential for MSFS, it can still make things smoother), Freesync or G-Sync, HDR, Display Port input and maybe a Game Mode then that would be great. TV’s also usually pay a bit more attention to audio quality than PC monitors (if they even have speakers at all), but a soundbar or hi-fi would still be better.
I specifically chose the 32in MSI MPG321URX 4K QD-OLED monitor to get the best possible visuals I could in the space I have available. It has DP, HDR, 0.03ms response time & 240hz refresh rate. It definitely makes MSFS + Tobii 5 smoother, but it was way over the stated budget here when I bought it.
If you can find a 32in or larger 4K tv which is in budget, has some gaming features and maxes out the space you have available, I don’t think you’ll be disappointed.