Ethernet

I am also interested in this issue, as building a new system and considering the Lumin T2 with Roon.Beside the quality ethernet cables I was recommended to add a fiber optic bridge or isolation between the router/switch and the Lumin, for example 2 Sonore optical modules.
The Lumin X1 has a fiber optic commection built in, so I assume something similar would help with the T2 as well....?

is there a significant difference in sound quality between audiophile grade cables and switches as opposed to regular cables and switches?

Yes. Significant.

I had connected my Streamer-Dac box via ethernet cable direct from the router using a "generic" cable. Once I changed to an Audioquest shielded Cinammon cable the sound difference was immediately noticeable and it was a good difference. I suspect shielding was the big reason.