Yaarel
🇮🇱 🇺🇦 He-Mage
Yeah, the "Astral" creature type is the same thing as the "Outsider" as a creature type. Within the Astral, Celestial and Fiend are Astral subsets that specialize in ethical concepts. Even Aberration is part of it, albeit a kind of "Anti-Astral", like unconscious versus conscious. The Astral is the realm of ideas that form reality.I've gone back to using the 3E Outsider to handle anything that isn't elemental, fiend or directly celestial. That covers ethereal, astral, slaad from limbo, modrons from Nirvana, etc. Subtypes can be used to differientiate what plane they are from. So, for example a Blue Slaad would be Outsider (Limbo, Slaad), while a Modron would be Outsider (Mechanus, Modron). Great Old Ones get to be Outsider (Far Realm).
Meanwhile, there are plenty of Astral domains within the Astral Sea "islands" that are "concepts" within the Astral mindscape, but not necessarily ethical concepts.