Explanation
Creating a Share Group based on the sharing set created for the Customer Community User Profile is the best way to give support representatives access to Container and Case records owned by Customer Community users. Share Groups are groups of users who have access to records based on a sharing set. Sharing sets are settings that grant community users access to records that have a lookup relationship to their user record1.
Creating an ownership-based sharing rule, creating a criteria-based sharing rule, and relying on the role hierarchy are not options that can achieve the same result.