I make it a point to fly formation manually for a few minutes after a manual take off but then go to AP.
Apparently the leader chooses a specific speed to maintain rather than a specific power setting causing everyone to constantly adjust throttle. Why they have to make such wild, 0-100%, changes I don't know. Just a limitation of the AI I suppose.
Oh, and thank God for time advance! Some of those missions are quite long.
Yes at least up to 4x usually 2x but at least you do into the action faster.