[NVMe Performance] Which is the best NVMe Driver and MB Connection (M.2 vs. PCIe)

Fernando, I discovered in the cards swap that MSI GT 1030 (PCIe 3.0 x4 device) inserted in PCIe 2.0 x4 slot results on graphic card at 2.5GT/s and NVIDIA GP108 on 5.0GT/s, in front of both with 2.5GT/s if are inserted on PCIe 2.0 x16 slot.

Crucial P3 Plus NVMe is 5.0GT/s on both slots.

This info is taken from HWINFO64.

Can you explain this? Thanks