If you decide to go with SQL server as configuration store you will need to install a SQL server to host the GPOAdmin database you can also use AD/LDS that use to be the preferred method but nowadays we advise to use SQL specially in large environments
Quest uses the following criteria to define large environments:
•Domains with more than 500 registered objects that run searches on a regular basis.
•More than 500 registered containers.
•Containers with objects nested more than 3 levels deep.
These are guidelines and should not be considered as an exhaustive list.
Please refer to the Quick start guide and user guide
https://support.quest.com/technical-documents/gpoadmin/5.17/quick-start-guide/11#TOPIC-1859651https://support.quest.com/technical-documents/gpoadmin/5.17/user-guide