No, cpu wise there should not really be an overhead, as it just uses docker or podman to run the application in question. the only bottleneck i see could be host filesystems that are not supported by docker/podman and therefore could lead to slow file access in the container.

In the end you could use any distro which desktop you like (which could be Debian stable, or something immutable) and then get your applications from the latest and greatest with Distrobox

If you like web tools maybe https://github.com/Frooodle/Stirling-PDF could be something for you.

Another +1 for restic. To simplify the backup I am however using https://autorestic.vercel.app/, which is triggered from systemd timers for automated backups.

You’ll have to use http://192etc:port. So no httpS for internal access

This is not really correct. When you use http this implies that you want to connect to port 80 without encryption, while using https implies that you want to use an ssl connection to port 443.

You can still use https on a different port, Proxmox by default exposes itself on https://proxmox-ip:8006 for example.

Its still better to use (sub)domains as then you don’t have to remember strings of numbers.