Regarding streamer connection to LAN/RoonServer, here is the link to some “measurements” I did recently to compare 100mbps , 1gbps , EtherRegen and wifi on the RPi4 transport: Audiophile Switch Experiment Results
From my perspective, galvanically separating streamer from LAN/RoonServer brought quite significant improvement in SQ. I assume this is system depended as some folks might have streamer already galvanically isolated from LAN, or maybe they don’t have many noisy machines connected to LAN.
I have started years ago with cheap 100mbps TP-Link LAN optical convertors which did great job. Now i’m experimenting with EtherRegen and OpticalModule , but although i have 250+ hours on the ER+OM I think the SQ is still not fully consistent so I hesitate to compare it to the old TP yet. However when ER+OM has good moment it sounds crazily damn good 
(realism and better tonal balance - more even and better integrated all frequencies together (I can’t grasp how’s that possible yet)).