I believe they only affect the flight planning, fuel planning etc. that are available in the EFB itself. No relation to the sim settings used by the aircraft, menu interface or ATC.
You can access the EFB planner from a browser outside the sim, as I discovered yesterday. Just sign in with your game account:
https://planner.flightsimulator.com/
It has the same unit settings as the one in the sim, or some of them at least. I haven’t had much time to explore it due to being out for much of the weekend.