I could be wrong, but your best bet is to perhaps create the volume in Windows as a simple stripe. Not sure RST supports NVMe drivers?
Use Windows Storage Spaces or Dynamic disks for RAID setup on NVME drives. Only on certain Z170 systems Raid on NVME drives is supported for Intel RST.
i saw an article regarding z170 raid.
but do you think is only hardware problem?
intel RST as see in specification detail support nvme Download Intel® Rapid Storage Technology (Intel® RST) RAID Driver
Installs the Intel® Rapid Storage Technology (Intel® RST) RAID driver version 18.104.22.1689.
This driver supports RAID 0, 1, 5 and 10. The driver should be installed after the operating system has been installed. F6 and RAID BIOS configurations need to be performed prior to installation of this driver for proper operation.
This driver supports NVMe devices. ""
Yes, need of new chipset (with wider DMI channel), PCIe or M2 slots lanes used must be from chipset, not from CPU, need newest OpRom in MB BIOS - none of this available for older systems.
As you have mentioned, There is no RAID support for NVMe drives with IRST on the X99 chipsets, so you will not be able to use your new drives in a RAID configuration. That chipset does not have the PCIe/SATA remapping technology required for RST to support NVMe devices. IRST only supports SATA devices on the X99 chipset.
You can find more information in a related thread: Re: Configuration Question