If a game dips just below 75 fps (let say 74 fps), UE4 will wait one full frame before it updates the current frame. This cuts the frame rate to exactly 37.5 fps instead of the 74 fps.
If Vsync is disabled the game will run at 74 fps but it will also introduce screen tearing. High framerate is crucial to VR games so this is preferable over the 37.5 fps and no screen tearing.
I guess the best approach is to have vsync enabled by default, but if framerate drops below 75 fps for a few seconds Vsync should be disabled.
What do you think about this? Any other solutions?
And is it even possible to change Vsync at runtime?