I suspect the modified Sonore Opticalmodule within Small Green Computer SonicTransporter Optical I9 would provide better isolation from motherboard.
it’s the same isolation that you would get if you had the opticalmodule outside and connected via copper to the motherboard. To run fiber end-to-end, one needs to design the motherboard from scratch and don’t think anyone is upto the task (well, Sotm did but they don’t have fiber)
of all these yrs that I have been experimenting, introducing fiber not necessarily translates to better sound - it’s just sounds different. In most cases (in some of my friends setup and mine) I have seen a softening effect to a point where it mars out the details slightly.
you can’t go wrong with either the PF or the JCAT. Both are equally good. It’s just a matter to taste which one you like.