The terms "celestial" and "fiend" do not represent specific personifications of the alignments. They are simply races/species/etc that do not live on the Prime Material Plane, and have a racial tendency towards that alignment. It's equivalent to Prime Material races/species having a tendency towards an alignment, such as how Orcs and Goblins are considered "evil" as a race.
Individual members of that race/etc might have a different alignment, and the races themselves are not specifically singularly aligned either. Devils are usually lawful, Demons are usually chaotic, and both represent a wide variety of subtypes. Thus neither is specifically the personification of evil.
A better term might be "an avatar of [singular alignment]". An avatar of Good would only be interested in helping good creatures, striking down evil creatures, and encouraging neutral creatures to choose the side of good. It would have no interest or concern over law vs chaos. It would be a very flat and alien perception of the world to mortals, and likewise the avatar of Good would probably not interact directly with mortals due to the insignificant scope of power any individual actually has, on a cosmic scale.
Similarly, the closer to being a "pure" personification of any normal alignment a given Outsider race is, the less likely it would be to deal directly with mortals due to their "impure and unpredictable" ways. Even the most strictly aligned lawful mortal is disturbingly chaotic to a being from the far outer planes.
That said, if all you were looking for is simply a way to refer to the races, then just refer to them by name. Grouping them by alignments has its own problems -- "The lawful Outsiders" could refer to Devils (LE), Modrons (LN), and Archons (LG).