The Black Magic egpu is only worth it if you already own a first gen LG Ultrafine 5K display (long story), otherwise its a bit expensive for what it is, plus it isn't upgradable... I actually have the 5K but still haven't bothered.
Razer Core X is a good choice, there is also the Mantiz Venus which I use which has USB ports plus gubbins for an internal SSD, so it can be a one cable solution.
I pulled an SSD from one of my hacks and put it in a caddy and it booted straight into Windows no problems, had to run Bootcamp drivers to get Wifi and BT but that was it.
Its an odd time to be buying Vega, prices are quite high for new ones and the Navi cards are faster, cooler, and quieter... for about the same price or less, but as mentioned macOS support is yet to be implemented (it is only a matter of time though).
You should check out egpu.io for all things egpu related.