I'm running an Optiplex 990 and WD Black 500GB NVMe PCIe WDS500G2X0C with a PCIe adapter along with BIOS A24 and am getting read/write speeds of 1632 MB/s / 1496 MB/s. The computer recognizes the drive for reading and writing but I cannot boot from that drive (BIOS doesn't recognize the drive in UEFI mode, or in legacy mode).
Since 9020 BIOS support for UEFI NVMe booting appears to be broken, you could try what works on older Legacy BIOS systems without UEFI. It took me quite a while to figure out how to do this on my 10 year old Dell (which obviously doesn't have UEFI), but I'm currently booting Windows 10 on a M.2 NVMe SSD.
The trick with the 9020 is likely to set the BIOS options "Advance Boot Options" to Legacy, turn on "Enable Legacy Option ROMs", AND use a M.2 NVMe SSD with a Legacy Option ROM. The dilemma is there are only a handful of M.2 NVMe SSDs that have this. I only know of 2 with reasonably good performance:
Samsung 950 PRO - can be found used on places like ebay, note SM951 will NOT work for this
Plextor M8Pe - available new on places like Amazon, note M9Pe and M8Se will NOT work for this
Additionally, in Legacy mode, you'll need to go against what's commonly recommended and initialize the M.2 NVMe SSD as MBR, and NOT GPT. (If the SSD is already initialized, Windows 10 Disk Management -> right-click on left side of disk -> Properties -> Volumes can be used to check this.)
Both of the above SSDs boot in my 10 year old Dell (although the M8PeGN 1TB paused for about 2 minutes before proceeding with boot, which may be a problem specific to my system or because I didn't update its firmware from 1.04 to latest 1.06).
Anyway one of the above may be worth a try - I'd buy SSD from somewhere where it can be returned in case it doesn't work out.