Thanks Talonsbane@ColdDog to the best of my knowledge, you can use a U.2 adapter to M.2 slot with little to no slow down in performance as long as that particular M.2 slot is rated as PCI-E Gen 3x4 as most newer model motherboards tend to have.
Since I started this project my cost has increased a little.
Added to my build list...
U.2 to M.2 Adapter - for 1 x U.2 PCIe NVMe SSD - M.2 PCIe x4 Host Interface - U.2 SSD - M.2 PCIe Adapter - U.2 Drive
Corsair Dual SSD Mounting Bracket 3.5" CSSD-BRKT2
Samsung 960 EVO Series - 500GB NVMe - M.2 Internal SSD (MZ-V6E500BW)
Hopefully, that is it.