Set it in the nVidia control panel. I don't know that Gsync modules have good scalers (the hardware where the scaler would normally be is what the Gsync module replaces) so have the GPU do it instead.
Thanks, I set it to not-scale. Though, I also had to set the resolution there to 2560x1440. If I left it at 3840x1600 and opened say Fall Guys at 2560x1440, full-screen, it still scaled. I guess some how the monitor was still displaying 3840x1600 due to either Windows and/or G-Sync.