... I think you can also tab to go to the next unit.
Sort of. Towns are currently 'units' for the TAB key.
Re zooming, the game appears to have the same keys as GC2, PLUS and MINUS on the num pad are what I was used to using. But either the 0.22 beta or my kludgy installation of it is balky--keyboard zoom changes are much more sluggish than scroll-wheel zooming.
Re double-clicking, I think it should be reserved for opening dialogs or pop-ups related to objects. Double-click the sovereign, and get a proper character sheet, that sort of thing...