[Solved] To future eGPU users — do your homework first!
A Vega 64 will get you the smoothest macOS compatibility. 1080 Ti can get you more performance in some cases, but it requires some hacking to make work (and doesn't work at all on macOS Mojave at the moment due to lack of drivers).
2016 15" MacBook Pro - 2.7GHz Core i7, Radeon Pro 460 4GB, 1TB SSD
Sonnet Breakaway Box 350, modded with 650W PSU, with Radeon RX Vega 64