2018 15" MacBook Pro (RP560X) [8th,6C,H] + GTX 690 @ 32Gbps-TB3 (ASUS XG Station Pro) + macOS 10.14.2 [OliverB]  

System specs

-MacBook Pro 15 inch 2018, i7-8850 6-core, 32GB Ram, 1TB SSD
-External Monitor Samsung 2560x1440
-Mac OSX 10.14.2

eGPU hardware

Asus XG Station Pro
Asus GeForce GTX 690 Dual GPU
Sonnet Breakaway Puck 570

Hardware pictures

Installation steps

MacOSX:

-Use @goalque's EFI-Bootloader to enable nVidia chips. @mac_editor's purge-wrangler does the same job.
-nVidia WebDrivers are not necessary, as the Kepler Chips in side the GPU are natively supported.
-Only for the nVidia card something has to be done, Radeon RX 570 is plug and play from start.

(Note: The screenshot is taken by another mac, but the result is the same. Mojave is well supported with nVidia Kepler GPUs)

Windows:

I could not get it to run in Windows. Two times "GeForce GTX 690" appears in Device Manager, but one is always yellow banged with Error 12. Disabling devices doesn't help. If someone has a tip (or better some experience) about getting it to run, I would be very thankful.

Benchmarks

1) Synthetic Benchmarks

Luxmark 3.1	OctaneBench

.

2) Multi GPU Support in Davince Resolve 15 and Unigine Heaven rendered by two GPUs

DaVinci Resolve	Unigine Heaven

Comments

- This is great setup with a lot of GPU power and possibilities. I typically attach the monitor to the RX570 and the Dual-GPU serves as double processing unit
- MacOSX handles very well Dual-GPUs.
- This and all Kepler chips work very well in Mojave, they are natively supported.
- Unfortunately it won't work with Windows (so far).