First, the server should be good for managing that storage, it all depends on the number of concurrent jobs you will run, but in general it has a lot of horse-power.
About the policy, the main reason as explained is that the underlying array is always the same, so it doesn't make any different to split backup files of a chain over multiple volumes, as the overall I/O will always be the same. You are only increasing the failure domain to two volumes with no performance benefit.
In regards to the size of a vm, again the policy doesn't affect this, in order to store a VM in a volume, when using per-vm chains the single vbk file has to be smaller than the volume. Counting an average 50% reduction, the VM can be as big as around 30 TB. But even with performance a single vbk is NOT splitted among volumes.
EMEA Cloud Architect @ Veeam Software
Veeam VMCE #1