Customizing Admin Bar

What’s the easiest to remove “Themes”, “Plugins”, and any theme specific tabs from admin? I don’t want to remove menus, widgets, etc necessarily (other submenus), just certain items globally across all sites, but have the ability to locally activate them for clients with more experience with WP.

I may want to remove some more of them as well. We are beta testing a small group to get back their input so we can make the system user friendly as possible for novices.