A collection of links and articles related to using external graphics processors with a Mac.
To see the use of your external GPU(s), open Activity Monitor, then choose Window -> GPU History.
In Mojave or High Sierra 10.13.4 or higher, you can use an eGPU with your MacBook Pro while its built-in display is closed, although I’d see that as a waste of a perfectly good P3 gamut display.
You can also connect more than one eGPU using the multiple Thunderbolt 3 ports on your Mac.
The Sonnet 550 and 650 eGFX eGPU boxes will send a full 87W of power to a connected MacBook Pro. Many docks only offer 60W, which under heavy load will cause the internal battery to actually drain from lack of juice.