Thanks.
Also - are scrimmage kick plays treated any differently than fumble/interception plays as far as change of possession/ clean hands rule?
Yes, potentially.
If it is just a foul on R that falls under PSK, R retains the ball, with the basic spot being the end of the kick. If it's a foul on K prior to the end of the kick, it can be "tacked on" at the succeeding spot and does not have to be declined for R to keep the ball (also applies to free kicks).
Both of these scenarios require that R has possession at the end of the down. If K recovers the kick (or a fumble after it), then we have general loose ball enforcement as before. (Note - there's more to PSK than just that, but just to keep things general and simple since you don't need all of PSK to "tack on" a K penalty).