@Christopher Shehu If you don't want the "Users" group is enabled with "Workspace access" and "Databricks SQL access" entitlements, you disable all entitlements. Create separate groups based on your use case and enable the required entitlements.
Regarding parent user groups, a group can be a member(child) of another group(s). As per the screenshot, subgroup is a child of john_test_group and maingroup (parent groups). Hope this helps.