tried both 2 ranks and 3 ranks musketeers - i still prefer 3 ranks due to faster response time. i try to loose formation the unit if i have the space, so the 3 ranks doesnt really get more casualties from enemy fires.

must try the skimish mode if it improves the shooting rate.

IMHO, i wouldnt completely rely on the gunpowder units - ideally, you should also have some Pavise xbowmen as they are more reliable IMHO.