have you tried to set GSync to work on windowed and fullscreen mode?
I have a Freesync monitor and a GTX 1060 3GB and it works fine. Redout for instance has stuttering with both Lossless Scaling and Magpie, but all the other games, work really well with Magpie.
Still, for Redout you dont need FSR, it has some built-in great scaling, maybe Unreal engine TAAU, but it looks good whatever the resolution. (I set the game at 1080p on a 1440p screen, 1440 60fps works fine but the 1060 3GB gets a little noisier, not much, but I dont want that).
Also I play Redout at fullscreen and using the internal upscaler of the game 'cos HDR doesnt work in borderless or windowed mode with that game.