Faster e-bikes usually run at higher voltage. But higher voltage reduces range as well, because lower speeds are more efficient. So e-bikes running higher voltage will have less range unless significantly more battery capacity is added to compensate. This causes higher speed builds to be increasingly expensive for the same range that could be gotten from a slower e-bike. Therefore deciding on a build requires balancing several factors: Range, Speed, Cost, and Quality.
The oldest patent for an electric bike I've been able to find at the US Patent and Trademark Office is this one, by Ogden Bolton, Jr. of Canton Ohio, which was filed in September 1895 and granted three months later. You can see from these original diagrams that it bears an amazingly close resemblance to modern electric bikes. In the general picture on the left, you can see there's a hub motor on the rear wheel (blue), a battery suspended from the frame (red), and a simple handlebar control to make the thing stop and go. In the more detailed cutaway of the hub motor on the right, you can see there's a six-pole magnet in the center (orange) bolted to the frame and an armature (made from coiled wire, yellow) that rotates around it when the current is switched on. It's quite a hefty motor even by modern standards; Ogdon mentions "a heavy current at low voltage—for instance, to carry one hundred amperes at ten volts." So that's 1000 watts, which is about twice the power of a typical modern bike hub motor.
To be honest, this bike is really designed for city commuters or kids riding around the suburbs. The fact that it’s foldable will let you carry it on the bus, on the train or even on the plane. It’s just not designed for heavy riding, long distances or tough terrains. If you want something sleek and fabulous at a fraction of the cost of most other e-bikes, this baby’s for you.
I purchased version 2.0 of this device and the manufacturer has been listening to comments from users and making running changes such as the three speeds and the rear suspension. I am an XL size user (6'2", 230lbs) and recently returned from a 26 day cruise around Europe. I rode this little scooter on cobblestones, miles and miles through the Vatican, inside ancient cities and all over the streets of San Juan upon our return stateside. There was only one time it was less than ideal and that was going uphill, on slick tile that was wet from a drizzle. It still make it, just had to lean way forward to get weight on the front wheel.