As the title describes, limiting framerate has no impact in the main menu and also being in the garage the framerate is unlimited. I don't know if the cap works in the showroom, I don't get enough frames to know.
I saw that too, my r480 is putting out something like 340 fps on most of the menus. But strangely, the automatic fans don't speed up like they would if I was on track, so I wonder if there is any stress on the vid card at that speed?