They are just run from .sublime-package files rather than needing to be extracted. .sublime-package files are just renamed zips. Package control also leverages this just in case you were wondering.
In the console type in "sublime.installed_packages_path()" to get the path Package Control should install to. Type in "sublime.executable_path()" to find the location of the Default packages. Alternatively, I wrote PackageResourceViewer
to make it a bit easier to view files that are in the sublime-package format.
Just some references below that explain a bit more about packages in ST3.http://www.sublimetext.com/docs/3/porting_guide.htmlhttp://www.sublimetext.com/docs/3/packages.html