I'm playing on a 1080p 16:9 monitor. I felt that the games default 4:3 resolutions look a bit too small so I managed to add a command line to a custom executables via gog galaxy so I can play at 16:10 resolution (1680x1050) and the game looks pretty great now, full screen except some small black borders at the edge. So it's not as stretched out as a full 16:9 resolution would be, and in my opinion gives an optimal look for this game on a monitor of this type.

My command line in the custom executables looks like this,

-CustomResolution:enabled -r1680x1050x32 -CPUCount:1