Finder is fine, it's just anything that has some graphics in it. Standard web browsing or watching videos. I'll post an update once I get the eGPU tomorrow and see how it handles.
Yes, if it happens only in web browsers, it's basically "expected behavior." That happens to me on a discrete GPU at 1080p just resizing the MacRumors Forums window!
https://imgur.com/CMEq0qH