I think it's down to personal preference, so obviously do what works for you!
I have the triple-27" monitors @4k setup described elsewhere..
Left-side monitor is Slack and Discord, and sometimes a File explorer or other misc apps that usually live minimized (Spotify, etc)
Center monitor is my IDE and terminal, or whatever "main" app I'm working in at the moment (sometimes Lightroom etc)
Right-side monitor is work browser (we use GSuite so lots of various tabs in GDrive, Calendar, Gmail, Docs etc)
You can certainly do this all on one screen, but I like to be able to glance at those things while still having my main screen laid out for ongoing work.
I also use multiple desktops so I have one for work and one for personal, and I can swipe all 3 monitors over to a different workspace with one key command, which makes macro context switching easier.