for both games, the windows modes are in 4:3 and fullscreen is 16:9. the manual claims that all modes will be 4:3. I thought it might be an nVidia issue, but all modes still stretch the games in fullscreen. any thoughts?

The GoG version was developed under an old framework that is no longer supported. I have recently built new versions but as of yet have not been able to update GoG. In the mean time you can find newer versions on www.thelordsofmidnight.com/support

Full screen will be in the aspect ratio of the desktop with window being 4:3 like the original.