  The existing option (1X NVMe adapter in a x4 PCIe slot) that is already working appears best for just 1 x NVMe SSD. Putting a single NVMe disk in a 4X NVMe adapter will not make it go any faster as the SSD can only use a maximum of PCIe 4-lanes anyway. The 4X adapter with 4 NVMe SSDs in a RAID configuration will need the VROC key; otherwise it will work as 4 single SSDs each using 4-lanes of the total 16 available in the x16 PCIe slots.
Some options under consideration.  Currenly using the cheap option.  1) cheapie x4 pcie nvme adapter for one nvme drive 2) Dell Ultraspeed Quad x16 nvme pcie adapter 3) GC-4XM2G4 (AORUS Gen4 AIC Adaptor For one nvme ssd, would 2 or 3  be faster?
Best way to install an nvme in an T7910