VPN between Proxmox hosts and VMs: some advices

Hi.

I have some Proxmox VMs which are not connected in a LAN, and I wish them to communicate together through a VPN made with OpenVPN.
I with to use the VPN to insert hosts in a cluster and let VMs to communicate each others not using the public network.
So I'm thinking about the future OpenVPN configuration, and the first question which I want to give an answer is: should I use a bridged device (tap) or a routed one (tun) in OpenVPN?

The second question is: should I use two different networks, one for Proxmox cluster and one for let VMs to communicate each others? (I think yes).

Please note that I prefer to have a unique network on all VMs independently from the Proxmox host, because I with to have the possibility to migrate VMs from one host to other without reconfiguring its networking. I know that tap devices are affected by broadcasting garbage, so I'm quite hesitant about this decision.

Could you help me, please?

Thank you very much!
Bye.