The Blackmagic's support of the LG UltraFine 5K display is unique but the inability to upgrade the 580 GPU is a non-starter. Makes me wonder if the 580 was chosen so Apple would agree to sell it in the Apple Store. I prefer the design of the AKiTiO Node Pro. I have used it to benchmark various GPUs including GTX 1080 Ti, TITAN Xp, RX Vega 64, and Vega Frontier. I also like the Sonnet Breakaway eGFX box with the 650W PSU.
Be aware that, though Resolve and Blender can choose the eGPU's GPU for rendering, some apps ignore it unless its GPU is connected directly to a display and that display is set to primary.
Lastly, some GPU functions like Resolve playback with Noise Reduction are hampered by the eGPU's lower TB3 bandwidth compared to internal GPU's bandwidth. For example, the iMac Pro's Pro Vega 64 produces higher FPS than a Vega Frontier in an eGPU. And if both GPUs are selected, the FPS is lower than if only the internal Pro Vega 64 is selected.
Be aware that, though Resolve and Blender can choose the eGPU's GPU for rendering, some apps ignore it unless its GPU is connected directly to a display and that display is set to primary.
Lastly, some GPU functions like Resolve playback with Noise Reduction are hampered by the eGPU's lower TB3 bandwidth compared to internal GPU's bandwidth. For example, the iMac Pro's Pro Vega 64 produces higher FPS than a Vega Frontier in an eGPU. And if both GPUs are selected, the FPS is lower than if only the internal Pro Vega 64 is selected.