PWM frequency VS motor eRPM

http://kellycontroller.com/faqs.php

What's BLDC high speed model and ultra high speed model differ from standard model?

32-bit microprocessor, higher PWM frequency.
Standard model: 16.6KHz, 40,000 eRPM.
High speed model: 33KHz, 70,000 eRPM.
Ultra high speed model: 100KHz, 100,000 eRPM.
eRPM=Mechanical RPM*Pole pairs.
It does generate more heat because of higher switching frequency.

When will High speed motor option or Ultra high speed motor option be necessary for the motor?

Please note high speed motor option is only useful for high speed motor.
eRPM=RPM*Pole Pairs.
The standard controller can support 40,000eRPM.
What is the criterion for high speed motor?
When eRPM of the motor is above 40,000, we can call it high speed motor for Kelly controller.
The high speed motor option doesn't mean it will push the motor to get a higher speed.
High speed motor option means that it is capable of catching the hall switching time of high speed motor.
If the motor is 40,000eRPM below, the standard controller can tackle the switching signal from hall sensor.
The motor will run properly.
That is why we don't add high speed motor option to the controller for low speed motor, which is not used to increase RPM.
The speed is the inherent characteristic of the motor. We can not change it.
Just like resistance is the inherent characteristic of the resistor.
Similarly Ultra high speed motor option is only useful for ultra high speed motor(70KeRPM-100KeRPM).