I currently have an Intel NUC running ROCK, connected to a Bluesound Vault 2i directly via ethernet. Rather than using the Vault as an NAS, I back up to a 2 TB Samsung SSD and connect it directly to the NUC via USB as my main drive. The Bluesound’s internal drive is now the backup so to speak. This setup works flawlessly so far.
My question is, if I go to an external DAC (I am considering a Chord Qutest), would I gain anything by going direct USB from the NUC rather than just going the simple route and, using the optical out on the Bluesound (bypassing the internal DAC) to go into the Chord.? There is no ethernet on the Chord as far as I can ascertain and I know ethernet will limit higher rates.
The second option would require a lot more moving things around thus my question. Thanks.

You’ll be limited to PCM 24/192 via the Bluesound optical out, whereas USB direct will give you up to 32/768 and, perhaps, DSD if ROCK includes appropriate drivers (hopefully someone else will know).

Re the comment by @dhusky, I ran into a problem getting a NUC/ROCK connected to a different DAC via USB. I solved it by switching to a full version of Ubuntu running Roon Server. For me this wasn’t a problem because I am proficient enough with Linux to configure a box the way I want on a home network. But it’s possible this might be a different consideration for you if you find a direct connection via USB to be problematic using ROCK.

(FYI - My Ubuntu/Roon Server is connected via USB directly to a Mojo Audio Mystique V2 SE DAC. It sounds great but YMMV.)