pcie 4x4

I'd like to get an old T480 as close to PC Master Race mode as possible, and I want to know what creative ideas you have for doing that. And I'd like to know the best NVMe SSD for it. 1. Is it worth getting Gen4? That is, does the controller for PCIe only support Gen3, or something like that...

Hello! I was wondering if my M.2 4x4 SSD will work on full speed if I install it in a M.2 5x0 slot? or will it only work as an 4x0? From my understanding I can physically install it but I do not know ware the 4 lane split is. I dont know if any manufacturer does motherboard with 5x0, but mine...