Your workload (a NAS and a handful of services) is going to be a very familiar one to members of the community, so you should get some great answers.
My (I guess slightly wacky) solution for this sort of workload has ended up being a single Docker container inside an LXC container for each service on Proxmox. Docker for ease of management with compose and separate LXCs for each service for ease of snapshots/backups.
Obviously there's some overhead, but it doesn't seem to be significant.
On the subject of clustering, I actually purchased three machines to do this, but have ended up abandoning that idea - I can move a service (or restore it from a snapshot to a different machine) in a couple of minutes which provides all the redundancy I need for a home service. Now I keep the three machines as a production server, a backup (that I swap over to for a week or so every month or two) and a development machine. The NAS is separate to these.
I love Proxmox, but most times it get mentioned here people pop up to boost Incus/LXD so that's something I'd like to investigate, but my skills (and Ansible playbooks) are currently built around Proxmox so I've got a bit on inertia.