If you are using Veeam Backup & Replication with a VMware vSAN datastore you are probably following the Veeam KB 2273 (Configuration for VMware VSAN). But this guide is only limit to recommend the hot-add transport mode. So you are going to create several Veeam proxies because Veeam Backup & Replication chooses the most appropriate backup proxy to reduce the backup traffic on the VSAN cluster network. Maybe also one per host.