Exactly!
So allow us the option to put each 'split' on each screen AND another option to stretch the game map over more screens (if this is technically possible)
That is one way that might be able to deal with the issue. Many people here will be aware of different "view modes": windowed, full-screen, borderless...
I think that if the program is written in such a way that it recognizes the number of vertical and horizontal pixels over which the player wants to see the game displayed, that can help.
If Larian created a page where people could indicate their display setup (number of displays, resolution, refresh rates, maybe brand, colour space etc.) and how well things work / issues / comments that could be useful. It wouldn't take long to create or maintain.