So a number of months ago I picked up a Mantiz Venus eGPU enclosure in perfectly matching space gray for my 2016 15" rMBP and it worked great with High Sierra in OS X…minus clamshell mode not actually shutting off the internal display.
But Windows was a mess and basically I wasn’t willing to jump through scripts and patches and potentially wrecking the Windows installation every time I rebooted in order to get it to work there. It didn’t help that I’d gone with an AMD GPU which required even more resources than Nvidia ones. So I waited.
Finally got around to running the Windows 1709 update after seeing some random stray comment online about how they no longer had nearly as much of a fuss to get it going. It’s now super easy.
All you have to do is have your eGPU connected to the right ports of the rMBP 16" and disable the PCI-E x8 controller that runs the left ports and reboot. Bam. No more code 12 error, GPU just works. Running the latest update of the AMD drivers for Bootcamp from Apple Software Update within Windows, the control center now sees both GPUs, XConnect allows you to connect and disconnect the GPU, it shows which applications are running on the external, etc.
So now my Sapphire RX580 works flawlessly in Windows without any hassle and the graphics smoothness is 👌