Listening to Klopp and Pochetino interviews it is clear they adjust their teams for the opposition they are playing. Just how good would Arsenal be if we did the same !! Always been Wenger's biggest weakness, tactical shiteness/inflexibility.
As for tactics, a while ago loads of people were harping on about 4-5-1 being better than 4-4-2 and now the talk is 3-5-2 being the best. There is no best formation !! If you play players out of position they will be shite. If you play a formation that suits the players you have you will inevitably get a very good team performance.
Wenger's arrogance won't allow him to change formation and tactics, the problem is when you have 3 or 4 "sometime-ish" players in the team you will have brilliiant games followed by utter bullcrap. Welcome to Arsenal.