Here’s an answer (in order of questions asked) for California residents/visitors:
[answers reworded from ncsl.org]
1. Registration only for motorized bikes/moped not under Class 1-3 electric bike classifications.
2. Depending on the county and other jurisdictions, the speed limit of the moped or scooter is one way to determine if it can be rode in the bike lane/sidewalk/beach, etc.
There is a site (attached a screenshot for your viewing) where you can find the limits and restrictions on this E-bike ➡️Segway eMoped C80 (or for other types of electric scooters, bikes, etc.)
In the case of the Segway eMoped C80, this e-bike is classified as “Class 2 ebike”. In California, these types do not require DMV registration for license plates.