I had a eGPU box with a GTX 1060 for months, but was using it for Windows 10 and a zbook 15 notebook. Unfortunately there is no Mac support for NVIDIA but some users get it working themselves - never tried it as it looked a bit to cumbersome for my taste. On Windows 10 the setup worked great. Was able to play games like PUBG or Quake Champions with decent (Medium) settings at Full HD and a reasonable framerate (I believe usually 70-90 FPS).
But in the end I decided that I wanted to switch away from Apple and also sold my Laptop to buy a Desktop PC with more horsepower. My wife still has a rather new MacBook Pro, so if I want to fire up some Final Cut Pro or Garage bend I could still do it.
Was not sure if the whole setup of eGPU was worth it for me, it surely allowed me to play those titles which were not playable without the eGPU but I believe it would have been wiser to spent the money directly on a new PC.
But of course, with switching away from the Mac my case is a bit special.