You don’t want hardware raid. Some options you can research:
Some OS options to consider:
There are probably other software/OS’s to consider, but those are the ones I have any experience with. I personally use ZFS on Truenas with a lot of help from this YouTube channel. https://youtube.com/@lawrencesystems?si=O1Z4BuEjogjdsslF
If you want cheap new drives check out https://shucks.top/.
You can get used Enterprise drives on eBay if you want to got that way. Look for a seller with lots of sales, a good rating, and a reasonable return policy.
I would stay away from kubernets/k3/k8s. Unless you want to learn it for work purposes, it’s so overkill you can spend a month before you get things running. I know from experience. My current setup gives you options and has been reliable for me.
NAS Box: Truenas Scale - You can have UnRaid fill this role.
Services Hosting: Proxmox - I can spin up any VMs I need and lots of info online to do things like hardware passthrough to VMs.
Containers: Debian VM - Debian makes a great server environment as it’s stable and well supported. I just make this VM a docker swarm host. I managed things with Portainer for a web interface.
I keep data on the NAS and have containers access it over the network. Usually a NFS share.
For HDDs the best way is to think of them like shoes or tires. They will eventually fail, but they also may fail prematurely. I always recommend having a spare drive ready.