Positions is a mistery, i have a ML/AML that plays Best as MC that in His on position, and i have a triple role ST/AMC/AMC h plays wonderfull as ST, goog as AML but very bad as AMC that makes is SA of shadow striker usessel.
I also had a DMC that played better as DC that in His position, he even got MOM 3 times playing out f position.
You can play 3 players out o position, i hav seen that If you have 4 the possession seems to decrease a litle, but i can not confirm it with 100% garantee.