I prefer to work with a single large external monitor. If my device is a laptop I keep it in clamshell mode when attached to an external monitor. I find switching applications with keyboard shortcuts and focusing on one thing at a time has improved my productivity. Using two or more monitors made it so easy for me to get distracted. To each their own though.
I dislike plugging into a monitor because it I hate the chaos of resizing everything. When I'm on the large monitor I unconsciously expand things; then when I switch back everything is on top of everything else or expanded beyond the window edges or reflowed or what have you.
I say this having worked with applications where you truly need an external monitor: image editing (where you put all your extra palettes on the extra monitor, and DAWs, where timeline and mixer views take up a full monitor each. Programming isn't like that.