Hi,
Why no using "qm remote-migrate" (Cf : https://pve.proxmox.com/pve-docs/qm.1.html) ?
And for cluster it's not the speed that is important but latency for corosync (should be under 10ms).
Cf : https://pve.proxmox.com/pve-docs/chapter-pvecm.html#pvecm_cluster_network_requirements
For the...