Because the power is applied through the chain and sprocket, power is typically limited to around 250–500 watts to protect against fast wear on the drivetrain. An electric mid-drive combined with an internal gear hub at the back hub may require care due to the lack of a clutch mechanism to soften the shock to the gears at the moment of re-engagement. A continuously variable transmission or a fully automatic internal gear hub may reduce the shocks due to the viscosity of oils used for liquid coupling instead of the mechanical couplings of the conventional internal gear hubs.
Can I legally buy/build and ride an ebike that’s faster than 20 mph? Yes you can, but you need to know that the ebike is no longer considered equivalent to a bicycle and is subject to other state vehicular classifications. The definitions for electric bikes spanning 20-30mph, and 1-2 horsepower ranges, will vary from state to state, resulting in a no-man’s-land consensus about limits for motor vehicle definition. The common label for a 20-30mph, 2-wheeled vehicle with active pedals is a Moped. Other MVA labels include motor scooter, motorbike and dirt bike which may have equivalent power and speed performance, but do not have pedals to assist and move the vehicle.
Stöckli E.T. Urban Confort, made in Switzerland. It has SwissGoDrive motors and Samsung batteries. There is a 500W/17.6Ah combo that seems to be ideal for commuters, i.e. it has a 50km range using full assistance. In the USA, a similar product is available as Currie eFlow e3 Nitro (different motor and electronics). This model doesn't have a front wheel suspension, but comes with "balloon" tires that somewhat absorb shocks. Options are available through types: "simple"/Urban/CROSS and man/confort models. E.g. the Cross model has a front suspension, a 500W motor and no equipment like lights, fenders, etc. However, paying extra, you can compose your own configuration. If you commute using bumpy roads, then get a front suspension.