This is seriously impressive! Thank you for taking the time to write your process so thoroughly!
As a developer I have a question: Did you benchmark compiling anything with this machine?
I can't say for a particular project as your github link, but I can give compilation time on the project I'm working on.
For reference, on a Mac Pro 2013 (8 cores), it took 14m25s to build running macOS, 15m on Linux and 24 minutes on Windows
On a Dell XPS 15 9560, 29 minutes on Windows, 14m in Linux
On an iMac Pro 10 cores: 7m40s running macOS and 14m20s on Windows
On an iMac Pro 18 cores: 9m50s running macOS (don't have times for Windows)
On the Hackintosh with i9-7980xe, using default BIOS setting: 9m55s running macOS
On that same Hackintosh with the BIOS settings provided in the first post (for the Gigabyte Designare): 7m27s on macOS and 13m10s on Windows
The almost doubling of the number of cores made little difference on compilation time unfortunately.
For an interesting note, the real iMac Pro 18 cores, at idle the CPU is around 65C, and during compilation of the project the CPU overs around 95C during the entire time. This combined with the lower maximum frequency make the 18 cores a poor choice for developers.
Get a 10 cores, OC like crazy... Or if you have money, and *lot* of spare time to set it up, get the 7980 and OC like crazy