I feel like there is probably something to be said about how well particular languages work with less horizontal space - the more verbose ones out there might lead to code that is so long vertically, that a lot of time will be spent scrolling through it, unless you're using a vertical monitor for that.
Then again, limiting the line width to something like 120 characters should allow you to edit two files side by side simultaneously, or run into far less problems when using something like a laptop, as opposed to having large monitors, while also help people who prefer larger font sizes, so it should be better for accessibility as well.
I currently have about 4 monitors in total, 3 of which are 21.5" at 1080p and there's also one vertical one, which to me that seems like a pretty decent setup - being able to browse code, work in a terminal, preview things in the browser and maybe get a few filesystem windows in there as well seems to improve productivity, all without the tradeoffs that tiling window managers might incur (though mostly just the learning curve) or struggling with software that doesn't work well with less horizontal space.
Of course, the technicalities of getting such a setup working are a bit cumbersome too - i cannot afford one of the fancy VESA mounts, so instead two of the monitors use a DIY monitor leg that's basically one long PVC pipe with some 3D printed mounts and screws, another sits atop of the computer case to the side and the GPU I/O is kind of a mess, since there's occasionally an adapter in there as well (monitors with DisplayPort are more expensive, rather than VGA/DVI/HDMI).
Honestly, it'd be nice to sidestep all of that with something like VR, but we're not quite there yet in regards to the resolution, or may never really get there at a good price point, even if there are some really interesting projects out there: https://arcan-fe.com/2018/03/29/safespaces-an-open-source-vr...
Virtual workspaces (basically multiple desktops) might help mitigate some of the issues, though!