The bandana solves the everyday problem: the hair does not get into the eyes, and sweat does not flow down the forehead during jumping work. They don't wear it at competitions, it saves a dozen distractions per class during training.
The main thing is landing. The bandana should not put pressure on the temples and should not slide down when leaning forward. It is checked in one motion: bend over and shake your head. If it has slipped, the size is large.