27" at 1440p for me personally. But I have two as my two primary monitors. Then I have a crappy old 720p 24" and 10" I currently forget the pixel density of. I want to say 2k

For most people sitting at a computer, this is likely the ideal based on distance from, and size of, monitor

I never in a million years thought I would like this game. Then I played it and found it to be a truly wonderful flood of happy brain juices. Glad to see it still putting out strong updates