This confuses me as it reads as if turning on Vsync generates screen tearing. When using any of the sync methods you avoid screen tearing. While not using any sync the frame buffer is read even if it is not completed and the monitor now shows a bit of 2 or more frames if the GPU fps is higher than the monitor refresh rate. G-sync and free-sync avoid this problem by not having the monitor request a new frame but instead the GPU requests the monitor to refresh when the GPU frame buffer is done.