Thunderbolt 4 can do 40Gb/s, many of these cards would work fine with an external PCIe enclosure. Only the the highest bandwidth cards, like certain NVMe SSD's

Thunderbolt 4 can do 40Gb/s, many of these cards would work fine with an external PCIe enclosure. Only the the highest bandwidth cards, like certain NVMe SSD's, and network cards, need a full bandwidth slot.