Personally, I start from covering my weaknesses, but rather on a global level than on game to game level. What I mean is if my defenders are not very good, I usually use deeper Def line, defensive-to-normal mentality, etc. I prefer to win 1-0 rather than 5-4, so to organize defense my first priority. Once my team gets better (more quality players, players develop strong understanding, start to like each other, etc.) I start varying style a little bit. What I never do:
- change passing style by more than 1 notch from one match to another;
- change mentality by more than 2 notches from one match to another.
- change width by more than 3 notches from one match to another.
The reason is I feel that these 3 attributes require time to adopt. As if irl you ask Arsenal players to start playing long balls, which they never did, and midfielders are confused, strickers have no idea where to expect the ball, etc. Within one game I sometimes go ultra-attacking, but to me it's like I am saying "There is nothing to lose, Go and try to save the match", not like "Completely forget what I said yesterday and revert your brains".
As for the scout reports, I find them useful only when they something about the opposition weaknesses (defense is slow, stricker should not cause us aerial trouble, etc.). Other than that I think scout doesn't tell me much. I know that Man Untd have very good players and if scout says they play defensive all it means to me that they are aware of my strickers ability, but that I know anyway since their defenders are good.
Maximising Strenghts to me means using my players abilities right. If my player has low dribbling stat, asking him to run with ball often is like asking GK never pass and always dribble. But it has nothing to do with next opposition. If I face Man Utd and think that Ronaldo is the main problem, I may chose ML with better defensive attributes to help DL. If opposition DCs are strong but slow I will go with fastest STs. Though it would be nice to get more detailed report from scout and not spend time figuring out who is who