I usually set up my formation and tactics in order to counter opponents style and quallity.
I have never played with 3st on this game so I can't say form gameplay experience, but from tactical xp i know that managers use red arrows a lot, some of them too much. For me there is no point to add any red arrows on 3st formation because it is offensive itself.
Adding red arrows can expose your defence too much and your team could become vulnerable on counter attacks.
If I can win most of my matches using various 451 formations with normal mentality, then what to say for 3st...