Exactly the opposite for me, using official container images is a major time save.

The containers will store their data in volumes, and ideally those volumes are individual ZFS datasets. The containers themselves are stateless, and you can just boot them up with the volume to “restore” them.

However if you want to learn proxmox anyway this is a moot point anyway.

Some concerns:

• get multiple smaller harddrives and put them into some kind of RAID / zpool with redundancy. the drives will fail.
• there is absolutely zero reason to have a VM per service when a container will do. There are no advantages. But VMs will take significantly more resources and be harder to right-size. There is no restore/backup advantage using VMs.
• for that reason there is also no reason to use proxmox in the first place, unless you want to learn proxmox. Truenas scale for example comes with pre-installed k3s.
• I would get a separate hardware firewall because it makes easier to expand the network later.