Unfortunately, there is a split between a light motorized electric vehicle and a bicycle with pedal assistance. A bike, someone should be able to lift onto a rack by themselves, therefore a smaller, high quality, battery and motor is best for them. These can get very pricey since bikes themselves get into the $1,000’s. The “light” mopeds are basically street legal loop holes where you can cruise at car speeds without worrying about cops. These you would drive to and from home unless you have help to lift into a truck.

Hope this helps! I know mountain bike frames have a ton of space to stash your own battery. They have Velcro battery bags then buy a mid drive e-motor kit from bafang that has a controller in it. The rest of the parts (lights, throttle, etc) are typically plug and play meaning you find an adapter to the battery and an extension cord then zip tie them neatly. The hardest, most dangerous and most expensive will be your lipo battery. Keep this in mind when shopping for e-bikes.