The game looks great in this mode with no screen tearing, but the fps displayed in game show fps just like if vsync was off so I can see where the video card bogs down.
With my in game settings on this GTX 1060 the fps never goes below 60 which is what the monitor is running at 1080p. FPS typically show 90-400ish.
I always try to set in-game settings so fps never goes below vsync rate.
DX11 acts the same with stutters, freezes, etc. which seem to have no relation to fps being displayed in game. DX9 looks better but that's probably an illusion.
Just playing with it right now plan to turn it off soon. Will turn it back on after I make any hardware changes to see if any in-game setting need adjusted.