Hi
Long time I don't talk here
Your P&G have big (coreless ?) motor, I suspect you need way more power than MF_NG is able to offer, but I don't remember precisely what onboard reg offer, 10V 1A ?
That's probably why it's not smooth. For those motors you probably need 24V, with probably more than 1A in stall condition...you need good protection/limiter otherwise you'll blow drivers
About PWM "printer" noise, it's more or less intrinsic.
There is a lot of PWM motor driver, you can probably test some others and have better result ?
Side question, is't those Amek series loaded with VCA fader ?
Best
Zam