Finally I could enable the VDDC on msi afterburner.
I just enabled in the settings the unlock voltage case.
Know there is the VDDC toggle on MSI AB and I could reach 1238mv which is in GPU-z something like 1.225mv max.
Before I could only'reach 1075mhz stable with heaven engine with stock 1.175v which is 1,09v on GPU Z
Now I managed 1150mhz stable benchmark but not yet tested for long run.
I hope I will achieve 1200mhz with 1.25mv in GPU Z
Actually from stock 925mhz to 1150mhz, with heaven engine, represent an increase from 58fps to 68/69 which is +20% more!
I find that the memory overclock help with MSAA. For exemple, stock 1375mhz to 1500mhz = 41fps to 44fps with msaa x2 on furmark
Only issue with my card is that the second fan don't start before 83% of speed fan, it only start one second when I boot the pc then shut off