You should be getting only slightly worse frame rates than you were seeing in UE4.
I do see various people with 30 series problems on this forum. Crashes, D3D device removed, choppy frame rates etc.
I assume Epic will figure this out sooner or later. In the meantime all you do is make sure your OS and drivers are up to date. Possibly downgrade to the studio drivers.
You might want to do some benchmarks to check it’s not a hardware problem, but that’s a long shot.
It could also be an engine config issue, also a long shot. You could re-install the engine, try a vanilla project, that sort of thing.