I checked the vpower.hk website and didn't see any reference to disc brake compatibility or a disc brake adapter.
http://www.vpower.hk/product.php?id=40
If you plan to use it with disc brakes you should probably email them and see what you will need and what issues there may be.


Also, I'll be very surprised if vehicle classification in NYC is based on current speed traveled and not on the speed the motor is able to propel the vehicle. You can use a cycle analyst to limit the speed.