so my experience with modern browsers' smoothness on Windows with a game running on one monitor and a browser on the other with a 2080 Ti:
Firefox: Youtube stutters badly when gaming
Chrome: no stuttering but scrolling isn't smooth (to be fair it's not smooth on Firefox either)
Edge using the original Edge rendering engine: no stuttering and buttery scrolling
Edge dev using Chromium: no stuttering and almost as good buttery scrolling as the original Edge