Downloading the reports through the API is probably the best approach for sites that don’t have the Data Explorer plugin installed. For site’s that do have the Data Explorer plugin, using it would be the best approach for getting the exact data that you need. Data Explorer queries can also be run through the API: How to run Data Explorer queries with the Discourse API.
On our hosting the Data Explorer plugin is not available on the Standard plan. We’re always happy to upgrade a site to the Business plan and get them started with a few Data Explorer queries.