I have a small apache case from harbor freight with a LePotato, mini router and a battery in it. I intended it to mainly be a road trip jellyfin/emby server (still deciding on which to fully implement) but I also have kiwix, Audiobookshelf and a simple nginx webpage to make getting to the services easier.
I've got 10 12tb Seagate EXOS drives in operation right now and have also run small capacity (2-4tb) WD Red and blue and Seagate Barracuda drives. For ssds I run Samsung 870 evos.
I've got six 2tb barracudas with 200k+ hrs and three with 80k+ I've only lost one barracuda over the years.
I've had nothing but bad luck with "recertified" drives or whatever Amazon calls them. One of the five drives I got off Amazon is still working, and that seller no longer exists. Server Parts Deals has been amazing for used drives. There are also discord and Facebook groups for tracking sellers and stuff.
Been considering building a mini lack rack to put on top of my lack rack to hold my mini PCs.
My cold storage is another Truenas box that powers itself up once a month, pulls an rsync and shuts down 2 hrs after that completes. Not quite what you asked for, but I don't have to think about it. The drives in that server are the smaller drives (2-4tb) that have been in the main Truenas box and been retired from that duty.
right now just the Amcrest app. Eventually I want to add more cameras and set up a NVR.
I have a couple MyPassports for cold backups and one I use for projects between my Desktop and Laptop.
I have a media server built in an Apache 1800 case with four 2tb 2.5" ssds in it.
If I where doing this, I would fill a hard case with nvme drives or 2.5" ssds and put 4k remuxes if you're dead set on 4k, or 1080p remuxes, the ones on my server are 6-8 GB. Yes, you can get super high capacity ssds, but they are real expensive. The reason I have 2.5" drives in my box was price. I paid $50 for each one.