Quirky means develop personalities; side effect of their type of ai operating system used. Yea they can fix each other (c3p0 gets put back together by r2) an astromechs are highly adept combat mechanics; imperial protocol droids mostly manage allocation of tasks and designating what resources go where while managing systems per those systems schedules ect. The astro mechs handle the repairs, moving things around with other more basic droids and also network security.