@biggen Right now, the only place we're using NVME in servers is for either cache in a hybrid storage setting (cache/capacity or cache/performance/capacity) or for servers with all NVMe.
Intel's VROC plug-in dongle enables RAID 1 in certain settings. That's driven by the CPU. Not sure Dell supports it.
For most applications, an R740xd with high performance NV-Cache and SATA SSD in RAID 6 will do. Intel SSD DC-S4610 series (D3-4610).
We have plenty of setups like that for virtualized SQL/database workloads as well as 4K/8K video storage.
EDIT: Forgot, in the Intel Server Systems we deploy we install a couple Intel NVMe drives, the VROC dongle for Intel only NVMe, and RAID 1 them for the host OS.