For under $800, I'd also recommend a Bluesound Node for digital output, if your primary goal is just Qobuz and you plan to use an external DAC.
There are definitely reasons to consider something like a Lumin D2 or some other streaming DAC all-in-one, including over the analog output of the Bluesound Node, but then you're also looking at a higher price point. Which may be fine considering the total cost of a streamer plus DAC? But your question is specifically about just picking a streamer for now.
Regarding if USB or coaxial S/PDIF would sound better or if they would sound the same, it will depend on both the streamer and the DAC. So you'd have to try with whatever you end up choosing to see if one sounds better than the other.