@jannem I don't think there's a clean solution to the sizing problem, just due to how ANSI works. anyways this may be what you want:
https://github.com/a-ba/squint
https://www.nemunai.re/post/xorg-duplicate-a-window-on-2-screens/
https://github.com/a-ba/squint
https://www.nemunai.re/post/xorg-duplicate-a-window-on-2-screens/