There are actions from that plug-in that will allow you to do one-off Spotlight searches (the results are not added to the catalog), but honestly the regular Spotlight interface is probably better for that.
The main value of the plug-in is that it allows you to create custom catalog entries based on a Spotlight query (instead of a specific folder location). Installing the plug-in doesn’t do anything to your catalog or results unless you create one of these entries. For example, I’ve always disabled the built-in Applications preset and created one using the Spotlight source that searches for kMDItemContentTypeTree == 'com.apple.application'.
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Rob McBroom