Some longer interval tests...
My 970/750ti test rig (linux, quark algo, 0.1 diff) reports ~27M with -g 3 setting now. It was 19M without -g parameter. But yaamp reports lower hashrate! It is about the half of the hasrate reported by ccminer. (13M vs 27M)
So the accepted hasrate decreased by 30%

It is a 3 hours average.
The situation is almost the same with -g 2 setting.
But as I recognized acceptance rate is 100%!