Six of one, half dozen of the other.
The '17 Roam 0 is a much nicer bike than a '19 Roam 2, as a bicycle. If you were planning on using it as such, probably worth the saw-off to make the switch. But if you plan to modify your bike to turn it into an underpowered motorcycle anyway, it will really make no difference in the long run, so I wouldn't bother. Do bear in mind, though, that if you make that modification to your new Roam 2 you will also sacrifice any Giant warranty, and possibly the dealer service committment.
There is an electric motorcycle sub-forum here on Bike Forums -- they are referred to as "e bikes", I believe -- you might ask there and get responses from folks interested in these motor vehicles.