It’s probably more important to consider what the resolution is compared to the size of the screen, as well as what the ratio is of the resolution.
The higher the resolution is for a given/same size of screen the smaller everything will look - but you will fit more things on the screen. And the other way around; if the resolution is the same but you pick a larger screen you will fit the same amount of things but they will look bigger.
And then for ratio the question is simply what you prefer. Computer standard is 16:9 or 16:10, which is 1920x1080 (HD) or 1920x1200. Ultrawide, which is what I have, is 21:9 which is 3440x1440 (UHD). Properly encoded movies shot at roughly 2.34:1 will stretch completely and filly my ultrawide screen properly, but will give me black bars top and bottom on my older 1920x1200 monitor.
I would suggest you go to a computer store if you can and stand in front of different monitors at the same distance you would at home. Try to get a feeling for what it would be like working on a monitor. And then if possible get the best deal and make sure you can return it for store credit and upgrade to something bigger if you need to (for extra money).