I was going to optically isolate the signal from my router to my streamer with a set of fiber media converters (FMC), but I’m thinking that this kind of internet service would eliminate the need for the FMC’s?
Just having fiber internet service does not obviate the need for further isolation downstream. You’ll still need to deal with noise from the router, etc. We switched from Fios (fiber) to T-Mobile because the former was way too expensive and the latter was offering 1-gig speed for only $50/month and we’ve been very happy and don’t miss Fios one bit. FWIW.