For those who did not see this epic post here, please look it up, it solved the problem so that you can genarally keep G-Sync activated:
You have to make a little adjustment in the nvidia driver settings, adding a separate rule for Cubase.
In the Nvidia Control Panel go to 3D Settings => Program Settings =>
- add Cubase as a new program
- got to “Monitor Technology” and set this to “fixed update rate” (don’t know if that is the right translation, I use the german interface)
- press the “Apply” button in the bottom right corner
Done 