I tend not to put arrows usually. For butterfly, the only type of arrows I would put are on the dml/r. If the other team have only fullbacks on the wing, I’ll use red arrows on them. Alternatively, if say you are facing a strong winger that is way higher Q then your wingbacks, you might want to use blue arrows.

I basically use arrows if I dont want/cant play a player in a position I need. So say if I am playing 4 at the back against 3 strikers but dont to play 5 at the back to cover the middIe striker, l would play a dmc blue arrow to act as my dc.