Is it okay to put Gen 3 SSD in my motherboards Gen 4 pcie slots?

with x16 PCI express socket) it will be also x8 PCI For your 653206-B21 HP DL380p560 Gen8 3 Slot PCI-E Riser Kit => but it

I have a WD black SN850 500GB in my _1 slot on my ASUS ROG Strix x570i mobo The only thing I can find in bios is set to _1 link = Gen 4

primal bet rockways slot Like USB, PCIe is forward compatible This means that a device which requires PCIe will work in a PCIe or PCIe slot Slot Size Lane Width

indian slot png  An 2280 solid-state drive , 22 mm wide and 80 mm long Connects to, Motherboard via one of: PCIe ×4; PCIe ×4; PCIe ×4