I also started with a Docker host in Proxmox, but have since switched to k3s, as I think it has reduced maintenance (mainly through FluxCD). But this is only an option if you want to learn k8s or already have experience.

If Proxmox runs on a consumer ssd, I would keep an eye on the smart values, as it used up the disk quickly in my case. I then bought second-hand enterprise ssds and have had no more problems since then. You could also outsource the intensive write processes or use an hdd for root if possible.

I put my storage controller directly into the VM via PCI, as it makes backups via zfs easier and I was able to avoid a speed bottleneck. However, the bottleneck was mainly caused by the (virtualized) firewall and the internal communication via it. As a result, the internal services could only communicate with a little more than 1GBit/s, although they were running on ssds and nvme raids.

I use sqlite databases when I can, because the backups are much easier and the speed feels faster in most cases. However, the file should ideally be available locally for the vm.

Otherwise I would prioritize logging and alerts, but as an experienced server admin you have probably thought of that.