eGPU still not there yet...

"For some readers, there were high hopes for Final Cut Pro. However, even when rendering traditionally GPU sensitive blur effects like Gaussian, Directional and Focus, there was no advantage in adding the eGPU with the GTX 1080 Ti."
barefeats.com/egpu_pascal.html

I'm interested in eGPU - with the announcement of High Sierra support for external graphics cards it could be promising. I hope I don't have to upgrade my iMac so it has thunderbolt 3 in order to take advantage of it though.

Some GPU performance will be lost using Thunderbolt 2 or 1 with external enclosure.