No AA's NRSAs get lounge access if they are in F/J as part of being in F/J
The AMEX plat requires a confirmed seat, so as long as your BP has a seat assignment you will get. Yes they have problems with revenue passengers without a seat assignment
The Citi Card will get you into the AC without a BP and your authorized users will get AC access as well.
it's a YMMV situation with priority pass, some will let you in, some will not. I have not seen a PP lounge turn a NRSA pax away, doesn't mean it doesn't happen.