By now, all writers are reading configurations of datasets, date dimensions and filters from Components Configurations API only. Corresponding tables in Storage API still exist and are updated even when they are not used for reading.
Table users is not used for reading nor updating anymore and information about users created by writers are stored in Writer's backend exclusively. You can access the data using API: http://docs.keboolagooddatawriterv2.apiary.io/#reference/projects-and-users-provisioning/users.
Table filters_projects is not used anymore, GoodData URIs of the filters were moved to Component configuration to section filters.
Table filters_users is not used anymore, information about assigned filters to users is obtained directly from GoodData API. Notice that it brings implicit obsoletion of sync-filters API call. The API call still rebuilds filters-users relations according to the filters_users table but the table isn't updated.
Last tables actively used by Writers are projects and project_users and they will be migrated soon, probably this week. They will be moved to Writer's backend similarly to users table.
Please don't delete configuration tables yourself, whole buckets will be deleted automatically when they won't be used anymore, probably within two weeks.