The short answer is there are none. The frames sold for shifters are the same as the ones sold for TaG. The difference is based on the stuff bolted to the frame. Besides the obvious difference of the motor, the biggest difference is that shifters alway have front brakes while front brakes are not legal in some TaG racing series. The rest is pretty much motor-related stuff, e.g., radiator, battery for electric start, axle keyways set up for different sprocket position, etc.