2018 MBP 15". 512/16/Vega 20.
(I should have ordered a larger internal SSD, but it wasn't really up to me.)
I have the internal SSD split into two 256GB partitions for MacOS and Windows 10. These work fine.
I have a Windows-to-Go Win10 install on a Sandisk Extreme 1TB USB-C SSD. This works fine - with an external mouse and keyboard.
Without the external input devices, I'm forced to use the touch bar for function keys, etc. The touch bar doesn't change context - swapping feature keys for F1...F12, etc. - when holding the Fn key. It displays all of the feature buttons (apologies as I don't know the term for these), but all of the buttons behave as Fx keys. So, I can't change the display brightness, volume (other than via the speaker icon on the task bar), etc.
I could live with that, but it's annoying.
The touch pad is the big issue. I can point and click. It does not however recognize two finger clicks, so I can't scroll or access a context menu.
To clarify: All of this works on the Win10 install on the internal SSD. It does not work when booting form the external drive. The internal SSD is hosting a Windows Insider version that I need for work. The external SSD has the latest public Win10 release.
Everything works fine under MacOS.
I've run the Bootcamp WindowsSupport install (obtained on this machine via Bootcamp Assistant) to get all of the drivers in place, and it claims to have succeeded. I have network, keyboard, AMD drivers and almost everything except for this odd behavior from the touch bar and the touch pad.
I suspect this is a driver issue, but I've not been able to install anything beyond what the Bootcamp installer provided.