I've got High Sierra Working, the nvidia driver (387.10.10.10.30.103) is not always smooth, but is stable, and I installed 10.12 (Sierra), because it's a easier, but then re-installed to High Sierra to get the NVME drive working (which is hella fast). Here is my EFI->CLOVER Folder. Hope this helps you boot. Do NOT install the CUDA driver, it left my system unbootable, I had to restore from backup.
The issue with the fan is that it is used to cool *both* the GPU and the CPU, by pulling air through the top of the chimney designed case through the sided radiators. Now if the GPU alway lags behind and then follows the CPU this (CPU Fan Header) solution is fine (tho, have not tried). However if you mine or do other GPU only intended tasks you run the risk of having a hot GPU (with a cool CPU).
I have had no success with the opencorsairlink software, but smckit reads the GPU & CPU temp, so a solution is very possible: to have a little daemon track the GPU & CPU temps and scale the fan based on the maximum. This daemon could control the fan via the unused internal USB3 port, and a small microcontroller.
This is the plan ... but for now i just have an extra fan on top of my device, when pushing it (ie. Compilation, Renders or Games). Temps are chill, noise is acceptable.
FYI, I have the 9...09-NA Model, WIFI does not work, BlueTooth trackpad does. Sleep gets randomly interrupted.