Thanks for the update. Would intel RST be able to make a bootable raid 5 array using m.2 drives if the motherboard supports it. such as this model from asus?
According to the latest brief (here: Intel RAID Solutions for Client and Enterprise), Intel RST has support for (a) bootable RAID 0/1/5/10 arrays and (b) up to 4 CPU-attached NVMe SSDs. Putting the two capabilities together would indicate that, yes, you can put together a RAID5 array containing M.2 NVMe SSDs.
In the case of this particular board, I see support for three M.2 NVMe SSDs, which is a sufficient number of drives for the implementation of a RAID5 array.
Hope this helps,