bearodactylWindows 8 still has visual affects from aero enabled by default, you can turn most of them off by going to control panel > system > advanced system settings > performance > settings and then clicking "adjust for best performance" (in visual effects)
Have you tried using fullscreen? It might be an issue with windowed noborder
It's an issue that crops up from a windowed application, a 144Hz monitor, a secondary monitor of any lower refresh rate, and DWM's forced double buffering + vsync (after researching, it's not triple buffering). When all of these cases are true, the issue crops up. Essentially, DWM has issues with 3D output at a higher refresh rate than the lowest refresh rate monitor on the system, because they're all being tied together. You don't notice the lag when the application isn't 3D.
From what I understand, what's happening is core to how DWM works, as a compositing window manager. Window contents are rendered as frames per-window. When DWM is in charge of vsync (aka not in exclusive, standard fullscreen mode), each time it wants to send a new frame to the monitor, it gathers every current frame from each window and composites them into a single image. With a 3D application, if a frame isn't complete, it ignores that frame and instead takes the last frame, giving the appearance of lag. The game still continues to render that frame and every frame in-between, so the measured framerate isn't affected, but those frames are discarded by DWM and so are never actually pushed to the display. The issue is, I believe DWM isn't pulling the last finished frame at the refresh interval of the monitor, but rather the last finished frame at the refresh interval of the lowest refresh rate monitor.
The solutions involve basically setting one of the previous cases to false. That means you can either disable Aero transparency or Aero entirely (and in turn, disable the double buffer + vsync), which isn't possible on Win8, or you can either remove any monitors that are less than 120Hz, or just run in fullscreen mode so that DWM has no control over what frames you send.
In essence, you can disable Aero transparency in 7, or lose multimonitor productivity by either removing the other monitors or running in fullscreen.
This bug is up to Microsoft to fix. They either have to fix the bug within DWM itself by using a true per-monitor refresh rate, on top of allowing incomplete frames for 3D applications (they should let those applications handle incomplete frames on their own), or make it so that applications can request exclusive refresh rate control for each monitor, so that DWM doesn't manage it on monitors with 3D applications running. This second method would be the best, because the graphics driver could handle this refresh rate timing for the application, in case an application doesn't support it. It would also mean that GSync displays can have the exclusive refresh rate control that they need while running games in a borderless windowed mode.
NVIDIA needs to contact Microsoft about this while they still have open communication regarding DX12. It's probably too late to fix this in Win8, but they can at least get it set up for Win10, especially if the DirectX team and NVIDIA want to push VR so much.