[Freiwillige]

Keep in mind that the 2 20mm's that the Fw-190 removes from the wing are the older slower firing MGFF from the 109E series. So the loss of two less effective (Lower rate of fire, Lower muzzle velocity) MGFF's in trade for four MG151 20mm's is a good deal. Also the addition of 2 extra 20's is actually a larger deal than you think. 20MM's firing minenschloss (Spelling?) Rounds are deadly. And the drag isnt that much of an issue if you look at the context these aircraft were to be used in. The bomber interceptors were supposed to deal with the slow lumbering B-17's and 24's
and not mix it up with the escourts. The Luftwaffe usually had one flight to engage the escourts and two others to go after the bombers.

Hope this helps!