RE: High voltage single motor ESC
Some electric cars still come with mechanical speed controllers, but they're not very common anymore.
The advantage to an ESC is that you get more precise throttle control and better energy efficiency. Mechanical speed controls rely on several resistors to change the amount of voltage supplied to the motor which determines how fast the motor spins. Usually there are only two or three resistors so you only get 3 or 4 motor speeds.
An ESC is much more complex, and delivers thousands of small pulses of the full voltage to the motor to control speed. The more pulses the ESC sends, the faster the motor turns. There are usually about 250 points in an ESCs throttle curve, meaning that as you pull the throttle trigger the ESC increases the amount of pulses it sends to the motor 250 times. This gives much more precise control over motor speed, making the car easier to drive.