Around the 70s or 80s, as a kid, I read much of a series about a sort of federation of interstellar-knowledgeable civilizations. They often ran into advanced but pre-interstellar civilizations that they had to contact gingerly. They had a sort of investigator or liaison who worked for them.
One of the worlds had a bunch of creatures who were sort of "modular," and would come together as new creatures then dissolve at will back into smaller, component creatures. In another case, they had made contact with a fairly primitive, mostly water world with huge creatures that were delicious to eat. Some company from the federation had managed to set up some country-club like resorts there, causing issues since there could be exploitation. Can anyone give some titles from this series, and/or the author?