I currently have a 1600 x 1200 monitor I've had for like 14 years or something. I can fit 4 games on a screen, but they are alittle small. I'm looking at other size monitors and resolutions. What are your preferences for multi-tabling?
I'm thinking of something like a 27 inch 1980 x 1200, but I think I may want more vertical resolution.

Could get the 1200p monitor and use both it and your smaller one at the same time.

Depends on what you like and what you want to pay. I have two HP 27q's which cost $300 and change each and have them side by side on my desk. I like them and have had them a few years now, but next time I will be getting https://www.amazon.com/Samsung-C49J8.../dp/B07CS4KF7J or this. https://www.bhphotovideo.com/c/used/1439971?gclid=Cj0KCQjwwOz6BRCgARIsAKEG4FXNppeLnXEcN6JSQnXtbTxmOLoo9QwmbWAN9C61OUQI78zS6AFMzqEaAk5mEALw_wcB

Since I play better with 4 tables (instead of more), my 13'' mac monitor is enough.

My personal preference is at least FHD (1920×1080 pixels).

1920х1080 quite enough. I recommend not to play more than 4 tables, but there will be 2 more tables, just in case. If you don't have vision problems of course

all those fancy words. i use my 70 inch tv and can play four games easily. Could easily do twice as many but keeping up is the hard part .

I think in addition to the size and resolution of the monitor, the video card also affects how many tables can fit (maybe).
On a machine without a plain video card, it could only hold a few tables (but let’s say it used to be different).