Is optical mostly a waste of time versus Ethernet?

You might want to read this article and the other linked articles.

If you are convinced there is low level noise coming over your Ethernet cable, you might try one of a variety of optical isolation devices near your server, such as the converters and fiber cable discussed here, to something like the GigaFOILv4-INLINE Ethernet Filter, which is an optical filter, to something more expensive like the Sonore offerings or maybe the Network Acoustics ENO or Muon, which are unpowered, transformer-based isolation devices. I suspect you only need one of these isolator solutions. The "audiophile" switch thing seems superfluous. I am currently running the GigaFOIL unit powered by a LPS at the end of my Ethernet cable run, close to my server. It seems to sound just as good as it did with all the other stuff connected.

@mitch2 These seem similar to the Uptone Audio EtherRegen and the GigaFOILand the Regen are pretty close in price.

One should also think in terms of PRE server and POST server In order to optimize entire chain. One may in fact benefit from FMC or ethernet filters on both sides of server. At one point I had FMC on both sides, this entailed 4 FMC, all with lps and pretty high end power cables, all connected to AC power conditioner.

The above extreme cleansing experiment, along with prior one with audiophile switch were not successful. My experience illustrates there may be fine line between sufficient and excessive cleansing.

Still much experimenting down road for optical vs ethernet.

In any case, add these devices one at a time, then over time optimize for that device. And do A>B>A comparisons to determine if device is really an improvement. I've been fooled by some devices in short term pre comparison phase.

None of this is "one size fits all."  The results/performance can vary depending on what is being used as a "server."  With my Mojo DejaVu server (and with the Antipodes DX3 I still own), I have the option to output an ethernet cable from the server to a separate Roon endpoint, or renderer, such as the Bricasti M5, Metrum Ambre, Sonnet Hermes, or similar.  In some cases, removing the renderer from the server unit can be sonically beneficial, but not always.    

I also have the option with both of the above servers to output USB directly from the server into my DAC.  In other words, both of those servers can also function as the renderer.  In the case of the DejaVu, the USB output board is the excellent JCAT USB Card XE, which results in the USB output performing at least sonically equal to using a separate renderer (when using the renderers and DACs I have tried in my system).  I suppose, I could try inserting the ENO between the server and the renderer to evaluate whether that makes a sonic difference.  

@mitch2 I'm waiting on completion of Taiko Extreme diy clone to experiment with. Initially, build will only have Jcat ethernet card, so used with streamer. Eventually, Pink Faun or Jcat usb card for rendering within server. Should be interesting.

Eno between server and renderer would be interesting vs. prior, at this point my experience is post server more important than pre. Upcoming Muon trial in pre server position will be my last attempt at pre server upgrades for time being.