for the bypass cap on the power supply you have some info here
PWM it’s with an external signal in PWM input, and the PWM pot ajust the level of signal in to zero to max , there should be no problem with that, I think you are talking about the PW pot
for PW pot you can add a trimmer pot on the pot for adjust what you want
(to pin 1 or 3 or both of the pot)