There used to be a way of changing channels - it's a radio - on 2.4GHz equipment if one got interference. Not is the equipment I have circa 2016. (5GHz is banned in Canada BTW so you made a good choice and is only for indoor use in the USA!) The FTC etc. rules for the new wifi router transmitters is that "it must be designed not to interfere and must reject interference." OK.
I just put down 50' as a crossover cable because I thought that would be an extreme case. I don't know is there is an optical version but that is moot because I haven't seen optical Ethernet adapters hardwired into consumer audio.
The leakage problem you mention makes lots of sense. We always found that if you have the right bandwidth cables and they were properly made, it was the adapter that was the biggest issue. Since I am just refreshing my knowledge of your system (and Ethernet) I haven't pulled out my manuals about jitter - I don't remember it being mentioned in computer courses on networking.
I could have told you not to bother with Powerline Ethernet for audio - it does have its utility - but I'm glad you found out on your own.
Is there a website where I can get a list of your current products and how they work with ancillary equipment and software? A block diagram of the overall chain and the innards to whatever extent you unveil would be helpful! I seem to be picking up bits and pieces and I don't have the overall picture.
BTW Accuphase has always used Ethernet "HD-Link and HD-Link 2" for SACD/DSD transmissions from transports to DACs and also other digital gear they make. http://www.accuphase.com/technical_information/dp-560_technical_information.pdf
This is all wired:
"The biggest feature of HS-LINKVer.2 is sending the music signal and the master clock separately to D/A converter in a receiver.
HS-LINK Ver.1 sends the music signal merging the master clock together, PLL circuit for master clock recovery is needed at receiver side.
Since master clock is been transmitting as it is, in HSLINK Ver.2, not only master clock recovery is unnecessary at receiver side but it comes to be free from the jitter at PLL circuit."