The Intel Optane SSD 905p is not a SATA Express drive. SATA Express is dead, and you will never own a SATA Express drive. The Intel Optane SSD 905p is a standard NVMe drive. There are models of the 905p that use the PCIe half-height half-length add-in card form factor, the 2.5" 15mm form factor with a U.2 connector, and M.2 22110 form factor. All are standard NVMe drives with a PCIe 3.0 x4 link. 
Last time I checked, compatibility with Intel's consumer platform bootable software RAID requires the drives to be connected to PCIe lanes from the chipset, rather than the CPU's PCIe lanes. On most motherboards, the M.2 and U.2 ports will be routed to the chipset, and if there's a PCIe x4 slot it might also be routed to the chipset.