The CXN digital outs are indeed unprocessed they are before the upsampling stage in the CXN, I use the CoAx one to feed my headphone amp.
The Qtest looks a bit short of inputs for what you want to do, I have never used BNC so I can’t comments. If you have to start looking at converters I would worry about signal degradation. USB would only work from a PC or Bridge device, not the USB ports on the CXN for sure they are inputs for USB Drives or input from a PC.
The manual doesn’t specify the hi res performance of the optical but that would be your best bet CXN Optical OUT to Qtest Optical in. I would ask CA Support if that will be 24/192 . The input is but no spec on the output
I know the Chord have a great reputation but so does CA , I would find a way to compare the two before I bought , you may find the improvement minimal , who knows but its an expensive experiment.
You won’t see a downstream DAC you will see the CXN v2 as a Roon Ready device , you will also keep the visuals on the CXN screen if that’s important. On the other hand using the digital INPUTS , not on your plan, you lose the artwork.
If you do go the Chord route , a CXN is a very expensive Bridge , some sale maybe called for
I am a CA fan !!