NVMe bottleneck
Most PC systems are severely limited in the number of available PCIe lanes which limits the number of NVMe drives that can run at full speed. For an ordinary PC adding even one NVMe drive to the PCIe 3.0 bus limits the graphics card to x8 connectivity instead of x16 without NVMe
(EPYC, Threadripper and the more expensive Xeon chips do not have this problem with PCIe lanes. EPYC has 128 PCIe lanes, Threadripper has 64, higher end Xeons have 28-40.)