Offside trap is a pile of trash and you should only use it if you want to concede. I've conceded more times with offside trap than I have without it, even with 3 defenders playing.

As for force counter attack, it's exactly what it says. You force the opponent to attack and then you hit them on the counter. Best to use with defensive although I like to use it with attacking mentality, I tend to get better results this way.