I dont think the height and weight makes any difference.

left and right does matter. For example of you have an MC and your MR gets injured your right footed MC will work better in this position than a left footer.

It also helps on free kicks and corners.

In regards to quality scores, you need to be careful as quality for a can be affected by the entire squad and therefore brought down by lower quality squad players. Ie the first team amy be a lot higher than the average quality suggests.

Also depending on how you load your skill points an average looking striker could have a massive attacking score and very low physical and defensive score.

Take this into account average means AVERAGE across everthing