I've been a multi monitor guy for a LONG time, mostly because I use a WM that benefits from it. But I recently moved and the company offered me a pick of monitors under a certain budget, so I decided to pick an ultra wide (34" 21:9) and a regular one (32" 16:9, I wanted smaller because I plan on using it vertically, but ended up preferring having two monitors with the same refresh rate), and sincerely, just the 34 is more than enough, since it arrived first I had to make due with it for a week so I built up some scripts to make it be seen as two monitors by the OS so I could use it as if it were two side by side and that was working great, and when I wanted to game just run my other script and it's one monitor again so it's the best of both worlds.
Given the chance in the future I would definitely go for a single 32:9, since I could even make it be 3 (or more) monitors with specific areas designed for slack and others for code, etc. That being said I'm not sure the same is possible on Windows.