@foone Yes! More monitors > More pixels, only because window managers do a much better job managing application surfaces in units of displays (or sometimes half-displays), than anything else.
ChromeOS's and Microsoft's WMs are reasonable at splitting a display into halves along a given axis, but no further. So if you have too many pixels on one display (say, 4k, which creates screen-sharing and window-sharing problems in video calls, and also webapps which don't want to use all that horizontal space), you can't conveniently and natively say "look, this app needs to be 720p, or 2080p, or even 1440p.
And applications are too often finicky when exposed to tiling window managers like ratpoison, awesomewm or xmonad. (I'm looking, no, *glaring* at you, #thegimp; you and #kde made dropping tiling window managers a practical necessity for me.)
Honestly, I feel like what we need is something like a tiling window manager, but which only ever constrains apps to predefined resolutions and permit limited aspect ratio variations.