Why do I need a switch?

OP,

Thanks for documenting your experimentation.

@curiousjim 

I really don’t hear any difference.

I am not surprised, and I agree with @tonywinga that you should either hear a change, or not - your perception is not likely to change over time. 

I have gone back and forth with fiber or Ethernet multiple times and as I said earlier, subtle changes at most, to the point where I doubt I could reliably discern the change, if there is any - they both sound good.

I never asked, were you trying to fix a problem or simply exploring possibilities to optimize your digital source?

@mitch2 

All of this started because I read a couple of articles and saw a few videos about cheap switches making a positive impovment in hifi systems.  So in answer to your question, I’m exploring possibilities.  I had a couple Netgear switch's, but for the life of me I can’t find them, so for $67, I tried another Avenue and bought the Ethernet to fiber boxes. 
In the same vein, I have read a few articles and watched a few videos about reclocking. It seems to me that it’s basically the only thing a switch does that could possibly change/improve the signal/sound. So, I was thinking about getting a Denafrips Iris DDC to do the reclocking job, but haven’t made any firm decisions yet.

@tonywinga 

So from the router I’m running a Netgear Powerline. One end is plugged into a UPS and the other is plugged into the same outlet my integrated is plugged in. It’s because of the Powerline device that I went with the Ethernet to fiber setup.  Maybe it could be adding noise. 
FYI, I can’t hear the difference between WiFi from the Nighthawk router and using the Powerline.

NETGEAR Powerline adapter Kit, 2000 Mbps Wall-plug, 2 Gigabit Ethernet Ports with Passthrough + Extra Outlet (PLP2000-100PAS) https://a.co/d/cKOpK93

So you are using some type of Wi-Fi device?  That changes the game.  

1) Put the fiber section between the router and the Powerline device and see if that sounds different.

2) Try to run an ethernet cable from your router to your music server with and w/o the FMC’s in the chain- if you can to compare the sound.

I bought a long ethernet cable and ran it from my audio grade network switch, which is after the FMC’s, to my TV at the other end of the house.  The picture looked so much better that I ended up working 6 hours running that cable through the walls and under the house to the TV.  Running an ethernet cable to the 2nd mesh router at that end of the house made the TV picture just about as good but since I had to run one cable to that end of the house it wasn’t much more to run two.