Is it the number of Watts (ex: 1000 W) or Volts (ex: 36V) that determine how fast the electric motor can go up to?
The unloaded RPM is the motor speed constant times the voltage. i.e. 80 RPM/V X 36V = 2880 RPM. The motor doesn't start to consume any significant electrical power or produce any mechanical power until it is loaded...
Also, bigger tire usually means faster speed on an electric bike. Smaller tires usually mean longer range. You can increase your range sometimes up to about 8 miles more just by going to a smaller tire. Like a 26" to a 20". There is a point at which if the tire is too big for the motor to spin easily then it can diminish your results.
Going to a smaller tire though decreases your speed though. And going to a bigger tire will decrease your range so there is trade-offs.
Morph.....your correct but only when speaking about a hub motor because you can not adjust for the ratio. Whereas, with a non-hub that is driving through the bikes gear system you have the best of all worlds. When you need torque or range you can gear down. When you need more speed you can gear up. Hey, that sounds just like riding a bike!