For all intents and purposes, PCIe and NVMe are interchangeable.  The system will have shipped with IRST (RAID) ON, but that still allows for both an NVMe and a SATA SSD operating separately.  The only caveat:  if you install both an NVMe (PCIe) and SATA drives, the NVMe must be the boot drive - meaning you will either need to clone the existing drive to the new one or reinstall Windows.  In either case, remove the SATA drive before starting the install or immediately before booting the cloned drive the first time.  Once complete, you can then reinstall the SATA drive and use it for storage.