Which is faster an slot or PCI-E slots for an drive?

Digitus 2-Slot NVMe SSD Expansion Card PCIe PCI-E x4 m2 expansion slot 2 NVMe PCIe x4 SSD Adapter for PCIe x16 Expansion Slot, accommodating four NVMe SSDs in a compact space with transfer speeds up to 64Gbps per drive m2 vs nvme slot Utilize an available PCIe x4 expansion slot for the installation, removal, or interchange of PCIe SSDs The drive tray accommodates M-Key NVMe SSDs

m2 slot screw Install in a computer or Thunderbolt expansion system x16 PCIe slot Sonnet 8x4 Silent Gen4 PCIe Card Installed in x16 PCIe Slot One Slot One Card 64TB