When configuring Veeam Backup & Replication in a VMware vSAN environment, the best practice is to use the Virtual Appliance transport mode. This mode is also referred to as "hot-add" and allows the backup proxy to mount VM disks directly from the datastore. This method is more isolated from the VMkernel network traffic, as it does not require network connectivity to the hosts to retrieve data, thus providing a level of isolation that meets the requirement stated in the question. The Direct NFS and Direct SAN options are not applicable for vSAN, and Network mode would not provide the necessary isolation from VMkernel network traffic.