PCI Express vs : Does it improve gaming performance?

Can a PCIe Device Work in a PCIe Slot? pci 4 in pci 3 slot After a quick Google search, I found this article which explains that: a PCIe x16 slot can theoretically hit approximately 32 gigabytes pcie 30 in 40 slot For example, the latest NVIDIA RTX 3080 PCIe gaming GPU should work fine in PCIe slot and not get a significant performance hit because,

pcie slot size I wanted to buy a Samsung NVME but I saw it was PCI-E 4 I know its fast, but its pointless if the laptop only has PCI-E 3,