On the left is native windows and on the right my last score with the virtual machine (the gpu wasn't properly detected, that happens sometimes though it does not change anything to the result, this is the best bench i got on native windows by the way).
I didn't play with native windows actually, as you can see on the picture there is almost no difference in graphics, the difference comes mainly from not having arch linux running at the same time than windows, thus allowing the cpu to take more load.
And as the difference is mainly cpu, even though it will impact benchmark i will not see any difference while gaming as i didn't find any game who could load my 8 cores at 100% (don't even know if that is possible with a videogame).
I will need heaven benchmark wheni have the time as it is almost graphics only, my guess is the difference should be less than 2%.
Also speaking of optimization, i didn't notice any performance gain with hyperv features, i'm thinking most of the tweaks we are doing mostly increase the vm stability and remove things like stutter, glitchy audio etc.
Following the example (and with some help) of someone from the mailing list i configured qemu hooks, that works like a charm and automatize every configuration one has to run before and after the vm process (mostly screen and processor configuration)