In 1 of my teams where 4-4-2 is the preferred formation I have an amazing MC who scores and assists more then an avg ST. I always red arrow him. On the left I have a well scoring ML/AML, I also red arrow him. My MC plays good on all 3 MC positions, so I post him on the right to keep some balance in my midfield with from right to left: red-flat-red-flat. For the rest I prefer to leave everything flat. I guess you could say that in general I look at player stats first, I would never red arrow an MC for instance who only scores 2 goals in 15 matches.

As for orders, I always use mixed for most things, mentality depending on opponents strength and counters on.