Just fyi the article you posted above says in the first paragraph:
“Even though Final Cut Pro X curiously doesn’t support external GPUs yet, DaVinci Resolve is another popular NLE that already works with eGPUs on macOS. In fact, the $299 Studio edition supports multiple GPUs, which can have a noticeable effect on both timeline and render/export performance.”
But to see it in action, here’s a screen shot of it running some 4k footage. But as mentioned, I had to purchase the studio version to enable that benefit. (Sorry it’s sideways, can’t figure out why it’s rotating after I upload it)
I hear what you’re saying that it’s a long ways off UE4 having this sort of achievement for free software, and on a Mac platform no less, I just was hoping it would also be a feature I could utilize given my ambitions with this new toy 
