14 CFR 103.1
The FAA currently does not discriminate between "VTOL" and "normal" ultralight aircraft, nor between gas-powered or electric. The aircraft, if powered, cannot weigh more than 254lbs "empty" weight excluding floats and safety equipment that deploys in an emergency situation.
I'm not sure what you mean by "peak limit" or "continuous operation". ...
No certificate needed and "satisfactory evidence" is only needed "upon request". From the FARs:
This part prescribes rules governing the operation of ultralight vehicles in the United States. For the purposes of this part, an ultralight vehicle is a vehicle that:
(a) Is used or intended to be used for manned operation in ...