It's more important the team you are against so if you was against villa away I'd attack them more than I would man city at home. It's about analysing your opposition and seeing what you think will work best in the specific game. Away from home I may change an attack player role to support as a...
I find attributes matter more cause you can work with them more, however you can sell a poor player with a good average rating for a lot more than he's worth
I find signing scouts from different nations helps a lot at improving scouting knowledge, I check under 19 national sides and scout all their players and also I generally just let my chief scout set assignments, it works well for me