My monitors are 1080p resolution, which is the same as standard TVs. It's good enough for casual use, but for a 'power user', more resolution is needed. More resolution means more screen space and more ability to look at more things at once.
4K is currently the option that gives the most space on screen.. a 4K screen has 4 times the number of pixels of a 1080p screen, so it can either be huge or maybe a smaller size but with enhanced image quality due to having a massive number of pixels crammed into a small space. But 4K screens are quite pricey and worse than that, they really need a top-end graphics card in the computer to be able to run 3D software and games on them. I don't play games a huge amount, but I do sometimes and I wouldn't want to lose the ability to play games just because I upgraded the screen. I think it will be possible to play games in a window on a larger screen, so maybe this isn't such a problem. Graphics cards are currently pretty hard to find and the two biggest computer shops near me have ZERO in stock, because crypto miners are buying them all up in vast numbers!
The other option is to buy a non 4K screen, that's bigger than 1080p.
Then there's the issue of the type of panel in the screen. IPS is the form that is meant to give the best colour representation, which is important when working with images and video. I am not a professional digital artist, but I do make images and videos - and sometimes for clients, so it would be good to have an IPS screen. Unfortunately, that also boosts the price.
Then there's the refresh rate (the speed at which the screen image is refreshed) - with lower numbers (in milliseconds) being better. If the refresh rate is too high (as with flatscreen TVs) then photo editing and gaming is hard to do because there can be a lag between moving the mouse and seeing the change on the screen. There can also be a 'ghosting' effect created (residual images).
Additionally, there's also the size/shape of the screen to consider. Some screens are HUGE - at over 50".. While the standard is 27" currently. So I could maybe get two 27" screens side by side, or one big one. There are also now the super wide screens that are one single panel that is as wide as two standard screens side by side! These are great for gaming, but they don't come in IPS as far as I am aware.
Unfortunately, these screens tend to be curved - which is no good for me as I need a flat screen for photo editing etc.