To be sure yes it would be best to hear from the seller but those thresholds are just TTL min high and max low specs just like you would expect for any PWM input. So if the laser can be turned on and off at that frequency then the average beam power will be proportional to the pulse ratio. Think about it like this – take a PWM TTL signal and low pass filter it. The output will be an analog signal proportional to the PWM ratio. The laser is just heating the material. The material will have a relatively long (relative to the 5KHz) thermal time constant. This will act like the low pass filter. Does this sound right?
The one thing that bothers me about the X-Drive is that the current is fixed 4.5A. I would prefer to be able to tweak it downward.