James, what exactly are you trying to do? If you want to use the Naim app to control the 282’s volume and switching, then you need to connect the ND5XS2 to the 282 with a 3.5mm jack cable.
The NDX2, like the ND5XS2, has only one RC5 output. Perhaps you were thinking of the 1st gen NDX, which had two: the advantage of that was that you could connect the NDAC for input selection, or a CD player, as well as the preamp.
Unless you particularly need to use it to control the NDAC, you could just connect the ND5 to the 282 so that you can use it for volume control and preamp input selection.
Cable between NDX2 and 252 does the job for volume and source selection on 252.
If we ever need to change nDAC input we can use 252 remote 7/8/9/0.
We found sources such as Sky Q sounded better going NDX2 → nDAC so now we route everything through NDX2 and nDAC input is never changed, so NDX2 remote is all we need.