No, don't turn backline to A coz that makes them push up. Turn it to C to make them sit back.
Offside trap should be B or C in this mode tho. If you play the offside trap so close your goal and the opposition spring it, you're buggered. Best to take it easy in that respect.
I would put your counter-attack to A if you are playing defensively tho. You don't want to attack with most of your players still back defending.