yes, I'm planning to add all the coaching values to the Players.ini, so it'd be possible to customize the way each player plays. That would fill many user requests at once..!
A negative Aim For the Line will raise the minimal distance to aim from the lines in all cases. A positive one will lower it, but only for the normal & short accelerations.
The Attack Will alters the likeliness for a player to do an acceleration on any ball, in a very close manner than the Defender attacks less often than the Power Baseliner.
Aim for the Lines shouldn't alter the ball-in-net ratio. You may have either a confirmation bias in action there, or a too low sample of strikes. (or maybe it could be from indirect consequences, by changing the whole rally flow ?
That Aim for the Lines raises or not the winner ratio will highly depend on the situation : if the opponent is fast enough to catch most balls near the line, then it won't have a definitive effect.