Hi, I'm an ex-Naim owner (Nait XS2)
I used Atlas Cables - Hyper 2.0 to speakers - no problems. The later Naim integrated are not as finicky with speaker cables as their older Classic series of amps were. I know many Naim owners also use Tellurium Q Back II speaker cables (further up the Tellurium Q range also)
As for RCAs, as you say, the choices are mind-boggling, but if you wish to use the Naim's 5pin DIN source inputs, Chord offer RCA to 5 pin DIN versions on a lot of their lines.
Maybe worth a visit to the Naim Community Forums to see what others are using. Many want to stick to Naim's prescribed NACA5, but it's an absolutely horrible cable to work with; stiff and unyielding. Which was why I used alternatives myself when I had my XS2.
Hope this helps. Good luck and Happy Listening 👍