I need larger monitors. Even a 16" monitor feels cramped to me, which either increases eye strain from high resolution, or mental load from having to visualize the things that aren't on the screen. Even if it's just an extra inch, that can reduce mental load for me by a lot. Make that a 24" monitor and it feels practically liberating.
But definitely only one, MAYBE two if I'm doing a fullscreen thing on one of them like media.
I'd be surprised if 16" didn't feel cramped to someone. I've used 3 21.5" monitors for over a decade now, and those are starting to feel small. Now my minimum size is around 24" at 1440p.
I found that it's really beneficial to me to have one monitor where the task I'm focused on is maximized to reduce distractions, and a second monitor where I have distractions and supporting information. So for example I typically have a web browser maximized on my right monitor, and at work I've got Outlook, Notepad, and Teams on my left monitor. At home I've got Notepad, IM windows, and folders on my left monitor.
The 24" monitor on my desk is about to be retired since it’s way too small. Currently looking at ~32 and above. The 35" looks like it’s the new standard, but that 49" has me intrigued.
But definitely only one, MAYBE two if I'm doing a fullscreen thing on one of them like media.