Astro, the more of your posts I read, the more I'm convinced that we are somehow cosmically connected!
Though I never completed the full process of organization, several years ago, I separated all my medical records by year and put them in individual file folders with the year noted on the label/tab.
These are the folders I have:
https://www.amazon.com/dp/b002hi9rkmFor years, I had the folders in a few boxes that were just big enough to accommodate their width, but the folders' hooks were inside the box and did not hang over the edge. I had enough folders in each box that the folders remain upright and compressed together from front to back. It wasn't ideal, but it worked well enough.
I should have used a banker's box: https://www.amazon.com/dp/B000NO06ZW where the hooks go over the side of the box and (sort of) slide in a little channel. Even better, some banker's boxes have a plastic channel into which the folders hook and slide. If sliding on just cardboard, the hooks will eventually tear into the cardboard.
There are also plastic containers like this:
https://www.amazon.com/dp/b00czokowiEventually, I bought two metal 2-drawer filing cabinets from Office Depot. While not the exact product, they are similar to this:
https://www.officedepot.com/a/products/7954627/realspace-soho-smart-18d-vertical-2They do a pretty good job and the hanging file folders slide on metal rails. They also have a lock and key, though it's certainly not high security. The cabinets metal is quite thin, but that can be an advantage when moving it empty. That's also an advantage of having two 2-drawer cabinets, versus having a single 4-drawer cabinet.
I'd prefer some heavy-duty, well-built filing cabinets like the company HON makes, but they are insanely expensive. However, the build quality is great and they use ball bearing sliding mechanisms, unlike mine that are just metal sliding on metal.
Actually, this looks decent:
https://www.target.com/p/hirsh-2-drawer-vertical-file-cabinet-22-34-black/-/a-52436947 It's more expensive, but uses ball bearing mechanisms for the drawer slides.
Around the same time I started trying to organize my files, I bought an inexpensive flatbed Canon scanner off eBay. I think I paid around $50 or so. I started scanning some of my paper copies into the digital domain, with the intention of having an alternate archive. Plus, like you suggested, I could file the digital copies in multiple ways. I could make copies of files and organize them by year or doctor or type of document (lab test, radiology report, etc.) or body part or health condition, etc. That's a lot easier to do with digital files.
For me, the idea is to digitize paper copies and print digital copies I download from my electronic medical record. Paper files have advantages, but are at risk of fire and perhaps a water pipe bursting. Plus, obviously, natural disasters like tornado, hurricane, flood, etc. Scanned documents use very little space, relative to the abundance of cheap digital storage that's available. Digital files are easy to protect, transport, and access. One could use a cloud storage service. Alternately, files can be stored on an encrypted flash drive and carried in a pocket or purse. My computer uses four hard drives in a RAID-5 configuration, so I'm less vulnerable than having a single hard drive. However, I also perform occasional backups to an encrypted external hard drive.
I hope maybe some of this brain dump might be helpful.