How does this game work is something that 90% of the players would like a definitive answer too. Trial and error is the only way to find out i'm afraid mate. Pick a formation YOU like and that YOU think is the best sign the strongest 11 for those positions and then tweek the tactics. Seeing what gives you more shots on target, goals scored/ conceded that sort of thing.
There is no right or wrong answer and if 10 people gave you thier formations and tactics chances are you'd get 10 different answers
By the way i agree the subs do take too long
Good luck on your journey