For more info about ssdpmenabler this you can read through this thread...
The Big Sur 11.3 update seems to have broken NVMeFix for me on my MBP 2015 with Samsung Evo 970 Plus... I used to get idle 0.00 A with both SsdPmEnabler and NVMeFix/Lilu installed on 11.2 . After t...
github.com
The author of Nvmefix reverse engineered ssdpmenabler after being told about it. After talking it over, he agreed to add this functionality to Nvmefix. So now actually you can just install Nvmefix with the aspm boot argument. Probably best just to run one extension or the other. See what works best for your drive.
For my drive, intel 660p, the nvmefix solution with the aspm command works best. I get the maximum power saving, no crashes, ect. nvmefix enables this drive to work very well with the macbook pro 15' 2015.