Unfortunately Proxmox doesn't use libvirtd, so Virt-Manager doesn't interact with it. It's designed entirely around using the web interface.

Your options here are to either stick with Proxmox without Virt-Manager, or use straight KVM. If you want a web interface for KVM, there's Cockpit, which is pretty decent for most basic tasks, but definitely a little lacking in advanced features, so you'll end up going to Virt-Manager for stuff like modifying virtual hardware. I think you can also use OpenStack as a web interface, but I've never played around with it myself.

Honestly, if you're a little newer to Linux I would probably stick with Proxmox, as it's a very well designed purpose built hypervisor.

For Docker, you'll want to deploy a VM and then setup Docker within the VM. Never run Docker from your hypervisor, it likes to fuck with IPtables in ways that break VM networking.

Seems like you’re nesting virtualization too much. Stick with 1 level of virtualization. If it’s a server, I’d use proxmox on bare metal. Its a server so split services per VM/container. Install OMV on its own VM. Another for docker, with docker services ran by a non root user.

Sounds like bridge mode is needed for the vm's network interface in virt.

I would say proxmox ve is easier to start with.

Install the proxmox iso directly on the hardware. Then setup a Debian without DE in a vm to run docker. Use Portainer to manage Docker containers.

Storage can then be assigned via Proxmox to the vm’s that need it.