I've used the razor core, akitio node and Aorus Gaming Box both work great on the Mac it was easier with the Aorus Gaming Box
on older non thunderbolt 3 Macs you need apple's Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter
https://www.apple.com/ca/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter
but on the 2016/2017 macbook pro's they work fine, there is a script(s) to run to make them work on the Mac but thats about it.
check the egpu.io forum for details.
I will say the Aorus Gaming Box was actually easier for me to get working on MacOS then under windows in bootcamp funnily enough. once you turn off System Integrity Protection its literally one line in terminal for the script to run, it even downloads the GTX10 series card driver (if needed for newer Nvidia GPU's) and then you reboot.
on the thunderbolt 3 macbook pro's I saw about a 5-7% drop in performance over native in a Mac Pro.
on thunderbolt 2 if on external display about 10% or 20%+ if internal
on thunderbolt 1 on external display about 20% or so and it couldn't game on the internal display due to bandwidth constraints.(but do have a workaround for that if any TB1 people are curious)
so eGPU's are plenty usable, the Aorus Gaming Box either with the 1070 or 1080 is probably the best price overall due to it including a GPU so they are less effected by crypto mining making GPU prices rise.
if you had a card or were going and the Akitio Node is the best price