I use an external display, but with mirroring on, so I can't answer your questions from experience. Looks like there is some support for external displays: https://github.com/koekeishiya/yabai/discussions/238#discuss....

> reliance on macOS’s accessibility settings to manage windows made them fairly limited

I think that yabai goes a bit deeper than other MacOs WMs; it gets you to disable (or partially disable) MacOs's system integrity protection, so it can use the OS window manager directly.