Yeah, i guess i'll investigate later this week and try the manual installation instead of the AUR package.
Edit: Ok found the issue, had to install optimus-manager and manually switch to nvidia with "optimus-manager --switch nvidia", nvidia card was install but not totally working (it was ok to use HDMI and displayport external monitors but not really active for gaming).
Now i'm 65fps in Glorious mode and 30fps in Absolute Maximum.
Oh and manually install mono seems to help too