I wouldn't bother so much with this bonuses, even with them at 10% i do not see them having any benefit during games. I did a lot of tests and my opinion is that they are useless.
Useless things i found in the game:
- training bonuses
- win reward
- condition
- morale
- most of the special abilities
- some of the skills ( for example GK punching and aerial reach )
- the in-game assistant manager
- player height, weight and leg preference
- other things i cannot remember now because it is late