Now how can I test this with Vsync enabled?
No idea, sorry. This thing uses Direct3d 11 but I have ever only studied OpenGL.

is reaching 147 FPS. This means that there is no Vsync enabled
Huh, I haven't noticed because it only reaches 39 fps on my laptop (and dies if I move the slider more than a tiniest silver to the right).

But if I chose lag reduction method "Query event" test application again maxes out the main thread entirely.
Hmm, system dependent, then. No such thing @ Win7 64 + i5 2450M + HD 3000.

Only the mipmap method is available for OpenGL anyway.