The Authority Control Documentation provides a good, basic overview of what Authority Control options are available in DSpace:
However, it fails to document any of the actual authority control settings/plugins, or how to configure them. For example, almost this entire (100 line) section of configuration options is "undocumented": https://github.com/DSpace/DSpace/blob/dspace-6_x/dspace/config/dspace.cfg#L1428-L1526
The only (very basic) configuration documentation on Authority Control is found at: https://wiki.duraspace.org/display/DSDOC6x/Configuration+Reference#ConfigurationReference-AuthorityControlSettings
This would be a good ticket for someone who uses authority control regularly and/or has local notes/hints which they could donate back to DSpace to enhance this documentation. Get in touch with Tim Donohue if you are willing to contribute to this area and need a wiki account to do so.