Although I am no longer part of the Naim world I have a very long track record of using their equipment. Their equipment has a reputation of being very sensitive to the type of cable used , not only in being well known for earlier generations of their power amp to speaker connections where the inductance of the cable played a significant role but also in regard to interconnects. The supplied Naim SNAICs often being the optimum choice.
Although DIN connectors can support balanced connection, the Naim preamps are entirely single ended so there is no advantage in using balanced wiring. So RCA /RCA will be your simplest choice now that Naim preamps have (some) RCA input ports. As for the best cable brands and in relation to my comment above, I cannot recommend anything in particular. The wires that I like best may not be applicable to your particular needs. It will be, unfortunately, a suck it and see situation. However there is a long relationship between Naim and Chord Company wires so you might start looking at them first.