Just wanted to share my setup and success with fixing 'error 12' since the posts in this forum were so helpful in getting it running, especially this post by @haruhiku.
This setup is with:
2016 touch MBP 15 inch - Radeon 460 4GB ram (I assume it would work with the 450 model as well), Razer Core, GTX 1070, Win10 Pro 64bit via Bootcamp.
I originally did the DSDT override with testsigning mode on since I didn't want to risk bricking this laptop that I use for a lot of my work. Overwatch was fine, but when launching For Honor I ran into an error with EasyAntiCheat not being able to run with driver signing mode off. So I switched back testsigning mode and we back to the forums to do more reading.
I ended up doing what the poster above did and just disabled various things in device manager until it worked.
Above: the things that I disabled that worked for me have the little down arrow next to them.
I am able to boot with the razer core still connected, the internal mbp display will freeze during bootup, but the external display will come on.
It will be a bit laggy and may blue screen and reboot once or twice, but once you are able to log in and go to display settings to disable the internal display (likely monitor 1), everything works great!
I just went ahead and changed power options so I can use clam shell mode, and am happy with the results. I can now attach the razer core, boot into win10, and close the laptop.
For Honor @2560x1080 - graphics maxed!
Hope this helps someone else!
I am able to boot with the razer core still connected, the internal mbp display will freeze during bootup, but the external display will come on.
Here’s instructions how to activate the iGPU:
automate-eGPU EFI ● apple_set_os.efi
Mid 2015 15-inch MacBook Pro eGPU Master Thread
2018 13" MacBook Pro [8th,4C,U] + Radeon VII @ 32Gbps-TB3 (ASUS XG Station Pro) + Win10 1809 [build link]
Good job! Very pleased I could help 
Can you be more specific about "disabling various things?" I disabled my AMD card and the screen went blank, restart didn't help, had to reinstall everything.
To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.
.If you look in the screenshot for device manager, the things that I disabled that worked for me have the little down arrow next to them.
Just wanted to attach an updated device manager screenshot for you. My 1070 is on the x4 Controller... not sure if that affects the performance or speed, or if it's different from what you're seeing.
