2015 27" iMac (R9 M390) [6th,4C,] + RX 5700 XT @ 16Gbps-TB2>TB3 (Razer Core X) + macOS 10.15.1 [Koncept_Zero]
27" iMac late 2015 17,1, (thunderbolt 2)
3.2 GHz Quad-Core Intel Core i5
1 TB Fusion
AMD Radeon R9 M390 2GB
MacOS Catalina 10.15.1
XFX AMD Radeon RX 5700 XT 8GB GDDR6
Apple TB3->TB2 adapter + OWC 0.5m TB2 -> TB2 cable
Display port cable to Samsung UE590 28" 4k monitor
Followed the steps outlined here: https://github.com/mayankk2308/purge-wrangler/blob/master/README.md
For disabling the SIP, I left out the "$" in the instructions linked above. This maybe code speak that I was to ignore regardless.
I bought this egpu purely for 4k video work in davinci resolve. This is really all I can benchmark. This is exporting a 1 minute h.264 4k file to 422 LT 4k without using optimized media or render cache. The 5700 XT ran this test in 2:40. The internal GPU ran this is 4:44. Using the same test as above, but with using optimized media and render cache, the internal GPU ran this same test in a staggering 0:36. The 5700 XT ran this test in 0:41. I also bought the RX580 and it out performed the 5700 XT in every export. Build here.
I also bought the AMDRadeon RX 580. In most tests, the 5700 XT performed worse except for the Unigine test. In Unigine, it blows the RX580 out of the water. But when I turned on Diablo 3, it was nearly as bad as the internal GPU! Also, the 5700 XT DOES NOT work with DR15! I had to upgrade to Davinci Resolve 16. This GPU's drivers have a long way to go and I just can't justify the extra cost nor do I want to wait for it to be optimized. I'll be returning it.