Now that I think about it, my SFF has the Radeon RX6400 which is PCIe4.0, but works fine overall. I did notice that every so often, the framerate very quickly drops to like 50, and then jumps back to 60 again. The system fans do kick on briefly, but then shut back off. Not much of an issue, but hey, it's an SFF.
I did find an RTX-2060 at a decent price here , but the specs might be a bit overkill for the 9020 MT. It'll work great with my main PC, assuming I can get it fixed. I'm probably going to stick with the GTX-1660. (probably Super since it's slightly cheaper than the Ti) I don't plan on running my games at max settings, and after looking through my library, pretty much all of them recommend 4GB or better for optimum play, so 6GB should be more than enough.