There is no way to "try" any Luna bikes, this is why I asked. Once sold and used, it is non-returnable, this is their policy.
Legally sold ebikes are limited to 20 mph on throttle, AFAIK. For 30 mph you would have to hack/reprogram the controller, and then it will require a license and registration.
Motors over 350W need disc brakes, yes.
If I were to build anything, hoping it to just "work" without giving me much trouble, I would rather choose a direct drive.