So I have a 2018 Superb. And the rear window wiper almost always vibrates when working. It seems to move too fast? Can that change the speed of this in the program? 

How old is the blade?  Chances are the rubber has hardened and it's not 'flipping over' as it sweeps across leading to the juddering (usually a tell tale is vertical bands of water left behind on the glass).

 

They usually go hard after about 18 months or so due to UV degradation and need to be replaced.