Re: VSync Question
You can only sync to one display device at a time. If you're using two, and they do not have the same mode, I'd expect there to be tearing on whichever isn't being sync'ed to.
However, according to your bug report, you're only using a single display device. Are you stating that if you export __GL_SYNC_TO_VBLANK=1 and run glxgears you're seeing a FTPS number significantly larger than 60?
Also, 1.0-9629 is no longer supported, please retest with 1.0-9755.