As a rough guideline, it’s easier to underestimate engine power than to overestimate it.
I’m using a normal electric engine on a two square scooter made of steel frames + hard plating + car wheels + storage battery. It’s like 300 kg + 120km/h without cargo, started slowing down badly around 700kg. Using large electric motor would be total overkill.
Because of this, you should never ever use extra light frames on any motorized vehicle, it’s just not worth it since weight saved is so little. Also always use seat over saddle for the same reason.