1. What is the size and resolution.
Size and resolution are dependent, if you have a 24-27 inch monitor, there is no point in going higher than 1440p, if you have something larger than 27inches then 4k might be considered. If you ever notice watching a big screen up close, you'll note that you can see pixels. A larger monitor and the ability to play in higher resolution is dependent on what the resolution will be. For 32 Inches, 4k becomes necessary unless you want to see jagged edges on certain things like text.
Depends on your viewing distance and your eyesight. I find 4K to require scaling, even at 32", at desktop distance. 100-110DPI with subpixel anti-aliasing is generally pretty good for general use with text at desktop distance,
for me, and both of my monitors (38" ultrawide 3840x1600 and a 27" 2.5k 16.9) are about 110dpi.
https://www.saji8k.com/displays/pixel-density/ has a pretty good chart of size to resolution (although they don't include 2.5k)
The type of light also affects the color output, but only if you're someone like me who likes vibrant colors in games will you notice such things. Most people don't notice nor do they care.
If you do any kind of graphic arts work, the quality of the color matters a lot. Getting a good wide-gamut monitor is possible with any of the the three (and most monitors come out of the box with terrible color calibration), although as you've noted, the true black is only available on OLED.
3. Refresh rate, how fast does the monitor pump out frames? The faster it can pump, the smoother it can look. Most people say 60 frames per second is good enough, I say it's only good enough if you're playing on a console and further than 5 feet away. If you are up close then animation quality is noticeable against a larger screen. So higher refresh rates are better.
As with other things, just depends on your eyesight and what you're used to. I don't see the difference, for what I do, even on a phone screen up very close.
The point is this, there is no point in getting a beefy computer if you don't have a monitor with a high resolution, high refresh rate. Why get a computer that can push 8k if you don't even have an 8k monitor to run it on?
There are a lot of reasons to have CPU or GPU power, and extra-high resolution (or high FPS at higher resolution) in gaming is only one of them. Or just a large CPU or GPU, separately - in my line of work for a day job, all you need graphics for is text, and integrated Intel graphics are actually preferable as they have the best driver support under Linux. OTOH, it really isn't possible to have enough CPU/memory.
I hadn't bothered to upgrade GPUs in years until I started getting into AI image generation.
