I find the AMD StoreMI and the competing Intel stuff to be very interesting... for example with the AMD StoreMI (not sure if you need both X470 boards and Ryzen 2000 series CPU) you can use an M.2 SSD in conjunction with another drive, then the software moves stuff around based on usage patterns.
i.e. 256GB SSD + 2TB HDD
You might be playing a GAME and see frequently accessed texture move from the HDD to the SSD.
StoreMI can also assign a DRAM cache (DDR4) though not sure how well that works.
INTEL just added support for secondary drives. Normally the SSD (i.e. Optane) is a COPY of the fast data (StoreMI moves the data but does not copy it which save space but makes backup a bit trickier).
Interesting to see how all this progresses... that may tie in at some point to the VEGA HBCC (High Bandwidth Cache Controller) to swap data in and out of VRAM as quick as possible from DDR4 memory.
I still don't understand the point of HBCC since system/VRAM swapping should continue to be improved in game engines to the point it's intelligently buffered before it becomes an issue... does this feature even work yet?