Can you explain to me why you have to reduce your frame rate to below your refresh rate with gsync?
And more to the point doesn't Gsync make high end cards redundant if all you have to do is maintain the refresh rate? There are many out there that still have 1080p monitor at 60Hz, 100hz and 120Hz monitors.
A /1070 TI/1060 will more then likely satisfy one's need for smooth game play. Which again is the point of having such a monitor. It mitigates the need for a faster video card.
Vsync adds a lot of input lag and also needs to be at a constant 60fps to remain smooth, anytime you using vsync and your framerate drops even by a few frames it gets choppy.
With gsync you don't get the input lag and your framerate can drop and still remain smooth.
You need to limit your frames with gsync because if it goes above your refresh rate it turns to vsync and you get input lag .