The prerequisites section of the Backup Agent installation documentation says nothing about hardware requirements. However, in the FAQ this entry specifically states there are hardware requirements:

Has at least 2 CPU and 3 GB of RAM above platform requirements. With each backup job it runs, the Backup Agent further impacts host performance.

The documentation for the Backup Agent in Cloud Manager has the same deficiency (see here for prereqs and here for FAQ.

We should update the installation instructions for all platforms for both Ops Manager and Cloud Manager to reflect this requirement. Note that this requirement exists for all versions of Ops Manager and Cloud Manager so the docs should be updated to include it in not just the current version but all previous versions.