Ryzen 4500 and Ryzen 5500 only support PCIe 3.0 as well.
The RX 6600 only uses PCIe 4.0 X8 so there could be performance loss if only in PCIe 3.0 mode.
The requirements I have read say you can run SAM in both PCIe 3.0 and 4.0.
Ryzen 7 7700X, MSI MAG X670E Tomahawk Wifi, Corsair DOMINATOR® TITANIUM RGB 2x16GB DDR5 DRAM 6000MT/s CL30, Sapphire Pulse AMD Radeon RX 7900 XTX, Corsair HX Series™ HX1000, Corsair MP600 PRO NH 4TB