I plan to use the 3.5"HDs to store expanded source trees, software/distro, and the complete EXR-stream renders of my output.
The EXRs are "intermediates". Regenerating them is expensive, but it is an automatic process, once the software is running.
I'll use the optical M-Disc media to store source files, PNG streams, video renders, and software archives.
As for the volatility of PeerTube, that's why I'm running my own instance, now.
Hopefully this works. 🤞