Is there a difference in meaning/usage between člověk' and 'osoba'?
Yes. They are different words. I would even go as far as to say that člověk=human and osoba=person, with a disclaimer, that Czech uses člověk (and plural lidé) in many contexts where English uses person.
Often you can use both in Czech. When talking about human evolution, it is only člověk, never osoba. A small step for a man is malý krok pro člověka. When you have a car for 5 persons, it is more natural to use osoby.