For your last question, I’m not sure the host bus configuration is recorded – you can see the entirety of what’s in a benchmark dataset by scrolling through the database, and I don’t see it. I suspect PCIE config does matter for a card on a given system, but that its impact is likely smaller than the choice of GPU itself. I’d definitely be curious to see how it breaks down, though, as my MoBo doesn’t support PCIE 4.0, for example.

I too would be interested to see how that breaks down. I'm sure that interface does have an impact on raw speed, but actually seeing what that looks like in terms of real life impact would be great to know. While I doubt there are many people who are specifically interested in running SD using an external GPU via Thunderbolt or whatever, for the sake of human knowledge it'd be great to know whether that is actually a viable approach.