Based on the given guidelines, the cloud administrator should select the Elastic DRS Baseline policy [1]. This policy is designed to scale the cluster automatically when additional resources are required, while also ensuring that application performance is not affected during the scaling operation. The Elastic DRS Baseline policy also ensures that resources are allocated efficiently and optimally [1], to minimize cost while ensuring that performance requirements are met.

For more information on the Elastic DRS Baseline policy [1], see the VMware official documentation at https://docs.vmware.com/en/VMware-Cloud-on-AWS/services/com.vmware.vmc-aws.sddc-management/GUID-FDD3A8AC-E42C-4B92-9C1D-8EB49D6C7129.html.