Macos do have a option to always show scrollbar. And I think this is a pre-requirement to enable that if you ever care about what your user may actually see as a FE.

Besides that, there isn't actually obvious different between firefox/chrome/edge on macos/windows.

The most problematic one is actually safari(which is on mac only). If you dev on chrome and use on firefox or vise versus. You usually get a "mostly work with minor visual different". But safari… will give you a fail and are't even usable. It is outright the modern age ie.