Several folks on the forum are using similar optical converters. Looks like exactly the same one you can buy on Amazon for $20. I hope they’re not charging much more than that for the audiophile marketing 
I’m using a Cisco switch with a built in optical interface connected to one of these adapters, which is then connected to my Vivaldi Upsampler with Cat 7. The company you linked does appear to provide power supply upgrades for the adaptor, so that may be useful. Of course you can also buy the Amamzon one and get your own linear supply for it. I’m powering mine with an Uptone LPS 1.2. I set this up more for fun than anything else. I can’t say it made any definitive difference to the sound.
Some folks swear by LAN tweaks and others use the most basic LAN setup happily. There are several threads on this forum already discussing this. Technically speaking no matter what tweaks you apply to your LAN the data will arrive exactly the same to your dCS component, it’s impossible for any tweak to impact this (in a positive way, anyway). The other argument for tweaking is to isolate electrical noise on the LAN from your component. Per my understanding the Ethernet specification alread does this, but as audiophiles we can’t help but try to do better