I have a vague sense of WWII pics and documentaries that you’d typically see M1 Garands carried muzzle up, but often see those with carbines carrying them muzzle down.
My experience with arms in WWII as an infantryman was that the M-1 was an aim and shoot weapon. When on the move and having reason to believe a/the target could be anywhere it was much better and faster to have the the butt close to the shoulder and bringing the front sight down. Of course for different people and different situations and different weapons scenarios change. My favorite weapon was the browning auto.