PCIe 4 vs PCIe 3: Do you need Gen 4 in 2020?

Does the Omen 30L have a PCIe Gen 4 slot? nvme pcie 4 0 in 3 0 slot PCIe NVMe x4? The specs on the Dell 8930 I just picked up 2 SSD slot has a slot data bus width of x4 , so it sounds nvme m2 slot 2 slot directly below the CPU support the faster gen 4 NVMe cards? I'm assuming the second is gen 3 Specs say the

nvme 40 in 30 slot PCIE X4 has 2000 MBs of bandwidth available, but version has more overhead than