Now back to decks. Yeah, those are 30 or more years old machines and can need some servicing. I have recaped 3 of my decks, not because it was necessary, but because they are about 30 years old. Some pots can be a problem, as you say and it's just to replace them. I start with checking SM and making a list of all parts I want to replace + some other things like soder wick, trimpots and so on. 50$ and P&P if free
Regarding polarized and bipolar caps, I do replace polarized with bipolar caps, only in a signal path where 0v is presented. I cant argue if it gives a difference but people say it's better with bipolars so why not. Of course, nothing wrong to replace with equal type. I think I'll recap my 2nd RS-B965 with the same as it came from the factory.