Personally I'd go for the ultrawide monitor. It's a far more elegant solution than multiple displays anyway,
You're one of those people who like constantly rearranging windows are you?
I used to use ion3 window manager because it, well, managed my windows.
With my current 5 monitor layout I again don't have to arrange windows, I just choose which display they should be on (everything maximised or fullscreened, text size ~175-200% in general, else I would probably only have the three)