You can mix and match plugins to extend your search, with the following caveats:
You can enable multiple data source plugins on a data source, or multiple results page plugins on a results page.
You can enable a plugin on more than one data source or results page.
You obviously can’t enable a data source plugin on a results page (or vice versa)
Custom-gatherer plugins can only be enabled on a custom data source, and you can only use a single custom gather plugin on that data source.