(assuming you want a better, faster product than the competition!?)
A 3rd non volatile caching tier:
Cache HDD to SATA SSD to NVME or Optane SSD.
Filtering by size and random/sequential:
Optane is fast at low que depth (QD1) random ~4K, but slower than a MP600 say at large sequential.
So cache the large sequential on MP600 and random 4K on Optane and read/write them simultaneously for an extra boost!
Simultaneous reads/writes to take advantage of drive type strengths:
If loading a game; start reading large sequential to small from the HDD (thats good at that)
Small random to large from from the SSD and/or Optane Drive
and have the reads meat in the middle, or wherever they meet...
that the eBoostr guys are able to do most of what I suggest above..! Talk to them!
4: Except for your deferred write RAM cache,
you cannot compete with the speed and 'intelligence' of Windows' Prefetch and Superfetch.
All you are persisting to do is BS the idiots you don't realise they're looking at RAM speed in the Disk benching software... and that said RAM speed is MUCH slower, with less cache hits, than what Pre/Superfetch get.
So stop! You just insulting the intelligence of most users nowadays with this outdated trick that lowers the respect and ups the distrust of influential reviewers and sys admins etc!
Make Pre/superfetch controllable/settable as windblows sometime thinks switching them off for SSDs is a good idea.
Use the data they use in the prefetch etc folders to better cache hits in the L2/3 caches too..!
Hell you might even be able to set/control their retardedly set Readyboost app to do #2 and 3 above...
Add an updated version of MyDefrag (15% faster than Windows' Defrag and anything else) to the package as a means of optimising the last level of the stack to further get optimal perf from PrimoCache...
Here also, you may learn a lot about using data in the prefetch etc folder/s effectively.
Running Primocache (or its files) through https://hybrid-analysis.com/
makes for some very ...'interesting' reading!!!
Why..!? Thats... really not necessary!??
Rather use that skill for the above '4: Instead' and charge more.