Well, there's a few things to consider with monitors. Ok, more than a few... I hope this doesn't come off as overwhelming.
- Monitors last a very long time - you may be using the same monitor after this PC is gone and you've built another one years down the road.
- You are going to be looking at this thing constantly when using the PC - you want the screen to be as comfortable and pleasing to your eyes as possible.
- Monitor preferences are EXTREMELY subjective. I may think something looks great, and you might agree with me, or you may think I'm out of my mind.
- Higher resolutions = more demand on the video card.
- Some people prefer higher resolution for a given screen size, and some are fine with lower resolution on that same size. For example, there are quite a number of people I've seen post who say that 1920x1080 is too low of a resolution for a 27" monitor, whereas I thought it was great. Similarly, both I and my son think that the 2560x1080 34" ultrawide monitor my son has looks great, where other will say that for a 34", that results in pixels that are too big, and you should go at least 3440x1440 with a 34".
- Ultrawide vs wide. Widescreen is a 16:9 aspect ratio, which is what TV/movies are mostly using. Ultrawide is 21:9. Some like one, some like the other. I used to think that ultrawide was a gimmick, until I actually used one. Now I feel like it's a "can't live without it" thing. The additional field of view that it gives you in most games is amazing, though a few games (not many) won't play nice with it. Still, that's my own personal opinion. Ultrawides are a bit more expensive than their 16:9 counterparts, though.
- Curved vs flat screen. Curved screens were another thing I thought were a gimmick. However, I find that with ultra-wide, it's actually very helpful. If you're running a standard 16:9 widescreen, I wouldn't bother with a curved screen, but if you're going ultrawide of 34" or more, you'll want a curved scree. Still, like the preference for ultrawide, this is my own opinion, and others may disagree.
- Refresh rate. This is something of a pet-peeve of mine. Honestly, to me, it seems that 60Hz (and thus 60 fps displayable) is just fine, though I wouldn't argue with 75Hz/fps. My suspicion is that the human eye/brain can't really register much more than maybe, at best 100Hz/fps, nor physically react to things that come that fast. There are quite a number who disagree with that, but I have yet to see any repeatable, scientific process that verifies this. What I have been able to find is that the fastest human response time was about 13ms, which equates to something on the order of 80-ish frames/sec.
THAT SAID... it seems that monitors that go up to 144Hz refresh typically aren't priced much more than their 100Hz and 75Hz counterparts. So, if the quality and price of two monitors is about equal, but one of them has a higher max-refresh, go for the higher max refresh.
- Adaptive Sync. The two technologies were GSync (Nvidia proprietary, and costs extra), and FreeSync (AMD, but based on an open VESA standard). It used to be that you were locked into GSync for Nvidia, and FreeSync for AMD, but Nvidia, starting with their most recent generations of cards, has finally officially started supporting FreeSync. No question here, get a FreeSync monitor. The wider the FreeSync range, the better, and LFC (Low Framerate Compesnation, used when the frame rate dips below the minimum number on the FreeSync range) is something I'd strongly recommend getting (not an absolute the way I say FreeSync itself should be, but strongly recommended). Basically what FreeSync and GSync do is adjust the refresh rate of the monitor on the fly, depending on how many frames/sec the video card is able to put out when gaming. This keeps things looking smooth, with no tearing effects.
LFC - only available on monitors where the max refresh rate is more than double the minimum refresh rate. Say for example, a monitor has a FreeSync range of 48-100Hz. If the frame rate dips to, say 45fps, LFC will set the refresh rate to 90, and display each frame twice. It gives the illusion of the refresh rate being 45Hz. Thus the minimum will effectively be half of what the lowest refresh rate is - so, in this example can handle things smoothly down to 24fps (half of the 48Hz minimum of the FreeSync Range)
IF AT ALL POSSIBLE - if there is a store within a reasonable distance of you that has a large variety of monitors on display, and that you can try out, I would HIGHLY recommend going there in person and trying. Reviews of monitors are all well and good, but your eyes are ultimately the best judge. In my case, there is a MicroCenter about 45 minutes away, and it was well worth the drive to find out that yes, I really do like how the large, ultra-wide screen looks.
If I were to recommend something off the cuff, I'd say go for a 34 or 35 inch ultrawide monitor,
with Freesync, with 3440x1440 resolution, with a FreeSync range that goes up to 100fps (or higher), and that has LFC. Maybe 2560x1080 resolution would be just fine for you as well, but, while I like that on the size of monitors I mentioned, I suspect that's a minority opinion. Definitely read up on reviews. Also, AMD has a database of FreeSync monitors
here that's pretty comprehensive, although the UI is a little bit clunky when switching sizes, brands, etc. that you want to filter on.
I know I've just thrown a
HUGE, possibly overwhelming, amount of info at you at once.... but a monitor is one of those things you want to be sure you're happy with, because you'll likely be living with it for a long time.