Is there a CLI that can display the package details such as disk usage, bandwidth quota etc?
You can utilize the WHM API function getpkginfo to see details about which limits or settings are defined in a package.
whmapi1 --output=jsonpretty \
Be sure to replace the pkg name "package1" with the desired package name.
Note: This API returns a hosting plan configuration. No information will be returned from the API if the specified package doesn't exist.