I don't believe the RNC is balanced (although I should know... I own one).
Unless I am losing it... I still don't see your signal chain in your posts.
As I see it, you will only use one side of the RNC for the application as you have described. No problem, there.
What kind of cable you will use depends upon the equipment and signal chain of that equipment.
In my earlier post, I described the "Y" cable you will use if you are using a mixing console and using the channel insert on that mixer.
This, however, is not the only way to record...
You might be using a preamp - then going directly to your sound card, for all we know. In that case, you would NOT need the Y cable... you would use two separate cables.