If you do not specify a set of resource pools to use, then Pano Manager uses all root resource pools. If you do not specify a set of datastores to use, then Pano Manager uses all datastores.
When there are multiple resource pools, the Pano Manager selects the resource pool with the most unreserved CPU. When there are multiple datastores accessible from the selected resource pool, the Pano Manager selects the datastore with the most free space.
VirtualCenter requires a datastore to be specified even when using a resource pool that is part of a cluster. In that case, you should specify the SAN/NAS datastore that should be used. If you do not, then the Pano Manager chooses the largest datastore in the cluster. If that datastore is local to a single host, then Pano Manager uses only that host within the cluster.
The Pano Manager keeps at least 512MB of memory free in a resource pool. This avoids problems with VirtualCenter where it may complete deployment, but not have enough memory to power on the DVM.