@tomas 1 is a 1080p 40" TV that comes with the apartment. It's rubbish at that DPI, so I use it for my music/videos — basically I keep only VLC, Youtube, and Audirvana there.
2 is a 4k 28" which I use as my primary. Chrome and Reeder are tiled, Finder makes an appearance when needed, Navicat (database) takes up the full screen when I'm working on that.3 is a 1080p 27" that I use for Transmission, WhatsApp, Telegram, and iTerm (which itself is for irssi and hledger). I also used to have an emacs org file todo list permanently open, but now it's just the meal plan. So this is the most static monitor, I guess, since I tile everything and nothing moves.
Of course, 3 monitors isn't necessary, really, but I get so frustrated switching windows and applications all the time that I just end up doing nothing, since pretty much everything I do involves referring to something else. That's why I was so unproductive over the winter holidays — stuck with 1 11" screen…