the above, with variations
I don't have any toolbars, just a menu bar with Preferences, but only because calibre insists Preferences be shown in a toolbar or menu bar.
I access my most commonly used calibre tools firstly via keyboard shortcuts, secondly via the context menu, and lastly via the Favourites plugin.
The Favourites plugin allows the selection of individual items from a tool's drop down menu, so for tools with lots of options (e.g. Job Spy) I only put the options I use into the Favourites plugin configuration. Same with Cover and metadata download from the Edit Metadata dropdown.
I'm mouse shy, so I drive the context menu and hence the Favourites menu with the keyboard arrow keys.
BR