30mph. And they recently lobbied the state to increase the horsepower limit from 2 to 4.

https://www.dmv.org/ca-california/other-types.php

They should rather keep the speed and abolish or sufficiently increase the power, as to keep the speed when going uphill.

Tell me about it. I was a scoot customer back when their scooters only had 2hp. I was routinely passed by cyclists when going up even a modest hill in SF.

Are they super heavy? 2hp is 1500 watts, way more than most cyclists can put out (few hundred watts).

Yes. Scoot uses a vespa style electrical "motor scooter", not an e-bike. I would not be able to carry it up my porch stairs and into my apartment. :)