Best eGPU setup in my opinion...stick with 10.13.3
After many days of headaches trying to get my eGPU working reliably on the latest versions of OSX, I finally caved and restored to my old 10.13.3 TimeMachine backup.
And it's GLORIOUS!
I'd forgotten how seamless everything used to be! Everything works PERFECTLY, ALL THE TIME, and I LOVE being able to use my internal monitor when the eGPU is active (the later versions all disable the internal monitor whenever I open a program that uses the eGPU).
Hopefully things get more stable for eGPUs once Mojave comes out of Beta, but for now, it seems 10.13.3 is what I'm sticking with. If you still have an old 10.13.3 backup laying around, boot it up. You won't regret it 🙂
Sorry 10.13.4/5 is better, it sports many eGPU specific features. You can accelerate internal display for metal and open cl software. Also there is a script to force eGPU use thanks to 10.13.4+ new plist