MacBook Pro (Retina, 15-inch, Mid 2015) + Sonnet eGFX Breakaway Box 650 (GPU-650WOC-TB3) + XFX Radeon RX 580 + Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter  

Hello everyone, just want to share my experience with my setup for the total cost of $591

MacBook Pro (Retina, 15-inch, Mid 2015) 
2.2 GHz Quad-Core Intel Core i7, 16 GB 1600 MHz DDR3, Intel Iris Pro 1536 MB, Catalina 10.15.3 (19D76)

XFX Radeon RX 580 (RX-580P8DFD6 / 1386 MHz OC+) - $159.99
8GB GDDR5, VR Ready, Dual BIOS, 3xDP HDMI DVI

Sonnet Breakaway Box 650 (GPU-650WOC-TB3) - $344.99
Power 650W, One Thunderbolt 3 port, includes a 0.7m 40Gb Thunderbolt 3 cable, AMD Approved - for the air-cooled editions of the AMD Radeon RX Vega 64, Vega Frontier Edition, and Radeon Pro WX 9100; NVIDIA Qualified - designed and qualified to support overclocked NVIDIA cards with high peak power requirements (Windows only)

Apple Thunderbolt 3 to Thunderbolt 2 Adapter - $49.00

Apple Thunderbolt 3 Cable 2 Meters (6ft) - $39.00

Let me start with why:

• X-Plane (expected to get more FPS on Hi-Res setting)
• Adobe Premier / After Effects (expected to improve rendering time & smooth it out during editing)
• Blender 3D (expected to improve rendering time & smooth it out during editing)

Actual results:

• Xplane (performance even worse than it was on Intel Iris Pro 1536 MB, dang, I should've read about X-Plane and ATI cards first)
• Adobe Premier / After Effects (smooth experience during editing, rendering is still using my Iris Pro 1536 MB even when the laptop is closed and set to use RX)
• Blender 3D (both experiences are okay)

Additional Issues:

• Every time when Mac OS Updates the PurgeWrangler stops working and you have to run the script again
• Annoying Static Noise coming my Sub and Speakers when eGPU is being heavily used (Furman Power Conditioner (SS6B) didn't help much) could also be to amplifying but I didn't have this problem before I got the eGPU. I have USB Soundcard M-Audio with two RCAs -> Behringer Xenyx 1002 FX -> KRK 10'' Subwoofer -> 2 x 5'' KRK Rockit
• Losing the performance with TB2 (it's pretty minor and would only help to avoid the issue #1 which is not something I can't fix)

Not like I'm extremely disappointed, but somewhat certainly I am, so I'll give my setup 5 out of 10. It was a choice: to build a PC or to get this $600 setup with keeping my Mac. Well, now you know how much I love my Mac and mobility. However, what I have learned:

• A $1000 PC with GeForce would serve me better considering my WHYs (consider your whys, read more before buy)
• F%^*ing breadcrumbs: Apple doesn't like Nvidia, X-Plane doest like ATI, other software doesn't use eGPU when should have
• I love this whole approach, but I'd give it 2-3 more years until it's more common and all more compatible

If you have any questions or suggestions, please reply, I'll be happy to chat.