Question: what enclosure did you get? I’m thinking of getting the Razer Core X myself, for an AMD card for bootcamp and macOS
There is an issue where I have to plug it in right after windows starts to boot because the mac tries to disable the integrated graphics if it's plugged in when the laptop boots (which causes windows to not boot). But if you don't plug it in while windows is in the early boot stages then windows doesn't seem to want to identify it. Apparently this is solvable with a custom efi module but I haven't explored that yet.
Otherwise it works solid in windows. Pretty much the same performance as when the card was in my desktop.
rEFInd successfully gets Windows to find the Intel UHD integrated graphics, so that's good. That let me uninstall the Vega 20's drivers and disable it entirely.
Even then, I still don't boot with the enclosure attached - it seems to ignore its presence? Unplugging and plugging it back in triggers Windows to go find all of the hardware, and then I have to wait 30 seconds while things grind to a halt as devices install. I'm eagerly awaiting AMD Navi 10 driver support in OS X, which I suspect will come around since people have found the names in kernel extension strings earlier this year.