At this rate might be faster to read code than a read me. Or convert to a wiki style if this much details are really needed.

I really like using Gokapi for this, like your own file paste bin to throw between PCs or send to people. Upload via link is development as well. https://github.com/Forceu/Gokapi

You can route traffic in different ways, for a high traffic endpoint hook an IP straight into nginx, while regular to via virtual opnSense router, that adds overhead but more flexible routing. Got PVE with virtual networking inside.

The cost of storage is always more than double the sticker price. The hidden fee is that you need a second and maybe a third one and a system to put it all in. Most our operational lab cost is backups. I can’t replace the data if it’s lost.