The configurations typically goes into the share-config-custom.xml file. The following is an example of stuff that you can configure in this file:
- Visibility of Aspects and Types (from custom content models)
- Metadata forms (from custom content model)
- Workflow task forms
- Document Library indicators, views, actions, and metadata templates
- Visibility of workflow process definitions (that is, what workflows can be started)
- Advanced Search
- Themes
- Menu bar
- Repository location
- Sorting fields and labels
- Web Framework settings
- Data Lists
- Cross-site request forgery (CSRF) policy
Note that a lot of the other extension points that require coding also involve configuration, so it is a good idea to read up on the configuration bit before starting any development with the other extension points.