I was running wifi all along and recently changed to wired connection to great effect. Removing the wifi card from the streamer/NUC gave a great boost to SQ. I don't use Tidal/Quboz, hence nothing streamed from internet but I do stream from a NAS.
My network is as follows
Cable ---> Arris SB6121 ---> Netgear Orbi Wifi Router ---> Edgerouter X SFP ----- fiber ----> eR (B) ---> Streamer
The NAS is connected to one of the A side port of eR (difficult to draw here).
The Arris/Orbi/Edgerouter is in a different room and there are couple of other network devices (like a Vonage router, a media server) connected to the Edgerouter. I run a long fiber connection to the audio room connected to the fiber port A side of eR. (I also have a Sotm sNH-10G loaned from a friend that I am playing with)
As you can see the audio path for the local streaming is all copper and isolated from the rest of the wifi network but I am not sure if its the optimal. I have ordered the SB8200 to replace the SB6121 to see if it further improves SQ - note, both 6121 and 8200 are BCM based but 8200 is DOCSIS 3.1 compliant. If the 8200 still makes an impact, it will be welcomed but I will have no idea why