shaliesh there are different types of card: there's the first (grey) one - balanced, attacking or defensive. You start off with this card, and as far as I can tell it doesn't have much effect since it controls style of play (which you obviously control in BAL).
The green cards are the one you can earn during BAL. These include one-touch play, one-on-one finishing, slide tackle, etc. These make your player better at certain things, so when you shoot they will be more accurate, for example. There are a lot of these cards to earn, and you get them based on your position and attributes. These cards can't be turned off, but you wouldn't want to anyway, they only make your player better technically and don't affect his style of play.
The red * cards, like anchor man, speed merchant etc. control how the computer controls your player in other modes, when you're controlling a different player. For this reason, they are irrelevant to BAL since you control your player all the time. You can't earn these cards therefore, and these are the only cards you can switch on or off in other modes.
Hope this helps