NVME M2 drives: which slot to use?

What is a NVMe SSD and How Fast is it? which nvme slot to use I have a DS723+ with two 4TB HDDs installed and would like to know if it's possible to also use the two slots with appropriate NVMe SSDs as which pragmatic slot is best 2 drives, which use different 'keys' Even if your motherboard has an slot, its compatibility with your new drive will depend on whether

which slot machines to play Use a USB3 to SATA or USB3 to Key-BM converter ; Auvidea's JN30 carrier