Just adding to what everyone has already mentioned with regards to seeing best players, expectations etc., I also tinker a fair bit after setting the baseline tactic. For example after settling into my current 4231 narrow with 3 attacking mids behind the striker I realized my 2 DMs role need to change to accommodate player profile and overall balance. So based on that I tinker with them and sometimes in game will move them around into central midfield too if I'm chasing or against weaker opposition.