Grits, the way it was explained to me was combat trim makes minute adjustments to your trim as your flying which normally isnt a problem, but I was told that if you disable combat trim you'll get better turn performance, less wing stalls, and your reverses will be better. Last night was the first time I turned it off while online and it seemed to make a difference for me.
Time will tell.
As far as the flaps go, I used flaps before but I only did 1 or 2 notches, last night I used the flaps all the way down and almost got a couple of zekes and a KI or two to overshoot me, I just wasnt quick enough to get my guns on them.