I have a single 1TB 3.5"HDD in my laptop, and several smaller USB 3 drives for backing up my data. As far as I understand Optane it's a software optimised hardware driven cache which utilises HDD space to boost system performance.Never heard of Optane memory until your post. Kind of a middle man between RAM and storage.. I thought funky things like this weren't made anymore.
Do you have large mechanical hard drives in your build then and use the Optane to speed them up?
It's certainly cheaper than RAM and it seems to work well for my needs.