All devices which are fed Ethernet must process the data packets and cache them into a buffer before reconstructing the data stream. The buffer acts like a solid state disk without the added complexity of file systems and disk blocks!
You mention using a completely different power circuit. For most dwellings, ’completely different’ circuits are joined together at the main distribution board which is often just a few feet closer to the power station grid. They are not really separate at all. My house is fed three phases, but all the single-phase circuits are joined to the same phase.
Strictly, wireless networks are not Ethernet at all. They obviously are more susceptible to interference from the plethora of other wireless transmissions and RFI.
Hardwired Ethernet is less susceptible but not immune. The topography particularly when crossing mains is important. Ethernet can be made 100% reliable by detecting and retransmitting faulty or lost packets, but this is not what streaming does!
Your Purist Audio Cat7 cable is built as shielded twisted pairs and many other cables are unshielded twisted pairs. The effect might be fewer corrupted packets but why this might translate into ’smooth and clean, just as the artist intended" is beyond me!
Not sure what this has to do with Ethernet switches, either ...