Side by side, long side horizontally. I move my chair and keyboard around a bit depending on my mood, but typically one is directly in front of me, and the other is to my right.

The one directly in front of me is usually for the "primary task", e.g. my editor if I'm programming, usually with multiple files displayed side by side. Sometimes also a single documentation browser window (other times just more editing panes). The one to the right for all the supporting stuff, (more) documentation, stack overflow, github, terminals running scripts that rebuild stuff whenever it changes, etc.

Thanks! I'm gonna give this a try today.

I've always liked an asymmetric layout when working with two monitors such that I have one "main" monitor in front used for my main task (e.g. my terminal for work) then a secondary to the side that is used for supporting windows - browser, music, pdfs, or another terminal depending on the work. It helps keep an established hierarchy, and you basically just use your neck as a window switcher.

When I had two identical big monitors with thin bezels I placed them side by side vertically. Then I had one marvelously big almost square monitor. In Windows it was not ideal, but workable. It not always worked as a single stretched space for everything, i.e. I had two task bars. If I could run Linux then I imagine there would be no problems also tiling window manager could be perfect.