If publishing is not enabled on the site then the Show Pages checkbox in Navigation settings will be grayed out.
If you wnat to include subsites of subsites in the drop-down menus on top navigation as the third or above layer then you need to modify the number of dynamic display links in the navigaton control in the site's master page.
The solution to have expandable tree view on the left-hand bar on SP pages is to enable tree view functionality on the SP site.
Testing the tree view has shown that the tree view on left-hand bar doesnt honor the Show Subsites & Show Pages settings. The tree view displays subsites but does not display publishing pages.
A known issue when modifying a top link bar in the non-publishing sites in order to adding new top link to the top navigation, the home tab on top nav doesnt highlight any more. The only workaround is deleting the home from navigation setting and recreate it. he detailed resolution can be found on link here.
