First is the pwm signal a 5V TTL level input - then you can use any free 5V pin.
Importnat is that only one feature get the pin assignes so either fan or laser otherwise they might change and overwrite signals.
For laser PWM is not supported only on/off. You need to add a event for laser intensity setting if you want to use pwm. Otherwise it is only on and off and you need to control power by move speed.