I use Kronos USB MIDI with no issues. Indeed, I have just stripped out a lot of MIDI cables from my studio and gone USB only where I can.
I don’t bother with USB audio though from the synths. Good old lime outs and Behinger Line mixers are still my audio route into my trusty old EMU 1212M which is still just about working with Windoze.
You already know how much I loved my 1820M from a previous discussion. I now have a desktop with many slots open, so I may have to try it soon. I have 3 of them just sitting around, collecting dust. I used to record on my ADAT and run everything through the 1820, into Cubase (very early, affordable edition). ADAT is still hanging around too. I feel like I own a museum. Sorry about going OT.
Just one piece of information I picked up today (product evaluations @ big T):
“Sorry, no further developments are planned on the K4EX even if support is maintained.” (source: Viscount support)
Not sure if I would go for such a product in a buying decision today. After all, it was launched in 2014…
OTOH: if it works for you as it is, why not? As long as you don’t expect any firmware updates etc…