I do not have any direct experience with Fiber Box II so I cannot say that adding a switch would or wouldn’t yield further improvements. It appears on paper that Fiber Box II is addressing and reducing the noise and jitter. Whether adding a switch further improves sound or not, this is something you would have to try in your system.
I have already stated my reasoning to audition SOtM switch, the 10MHz clock input and their newest CAT8M LAN cable with double filter block. Trying a fibre with SOtM switch has a slight advantage as it eliminates the need for one external converter box and LPS on receiving end. Again, i will be comparing copper LAN with Fiber to access which sound better to my ears.
As far as Taiko new products which include switch, router and re-designed network card; they are specifically designed to enhance performance of Taiko Extreme. And their availability (for now) is exclusive to Taiko Extreme existing and future owners. As per Emile, non-Taiko users will not get the full benefit, which includes a software / firmware interaction. If you would like to learn more about Taiko switch or router, I suggest you to check out Taiko Extreme thread on WBF.