What device is this? VP100 512GB, 4xSSDs in SoftRaid level 4? I'm not sure about RAID 4. Oh wait, I think you mean four 2.5" SSDs (in the internal drive bays?) raided with Softraid and only one VP100 in a PCIe slot?
I don't understand the difference in write speed for the VP100. Do you mean the script, when not executed by the launch daemon, only allows the read speed to exceed 1000 MB/s while the write speed was stuck at 500 MB/s? But when the script is launched by the launch daemon, it allows write speeds to use the full PCIe 2.0x4 bandwidth like the read speed? I don't think there should be a difference.
Does System Information.app still show 2.5 GT/s for the NVMe drive? If you used the EFI shell script to change the PCIe speed before macOS starts, then System Information.app should show the correct 5 GT/s.
#30
Also, the EFI shell script would allow the NVMe drive to run at 5.0 GT/s in other OSs (Linux, Windows) if they don't have their own method to correct the link speed.
I'm using 64GB from
https://eshop.macsales.com/item/OWC/64FB8MPK64GB/
The heatsinks are full size, like Apple's. I haven't checked the temperature. What app do you use to check the temperature?
I use maxmem=63488 in nvram boot-args to limit it to 62 GB to avoid slow down in macOS. I am looking for someone with 64 GB to verify that the slow down also exists in Windows 10 in Boot Camp and that the solution described at
#30 solves the problem for Windows.