Graphic Cards PCI 4.0 CARDS ON 3.0

I want to upgrade the GPU Only for my Ryzen 5 3600 , GTX 1060 system - and was looking at a RTX 3060 or RX 6700 (non-XT) and checked the specs to realise that both run on pci 4.0

How much of a performance degradation should I expect , if any?
PCIE gen 4 has a transfer speed twice as fast as PCIE 3 but that doesn't mean your FPS in game would be twice as much. In gaming you realistically aren't missing anything staying on gen 3
The bandwidth constraint is negligible and inconsequential. You should be able to comfortably run the RTX 3060 or the RX 6700 with maybe up to a max of 3% performance hit. Don't quote me on this remember seeing a Linus video a while back on this subject.