As far as I can tell, if the Ardling lists as options the ancestries from Celestia (Aasimon), Elysium (Guardinal or Beast Lord), and Arborea (something like a dryad-treant), then this Ardling would have a similar feel to the Pathfinder Aasimar. Other ancestries can be added later, like from Bitopia. Meanwhile an ancestry from a specific creature like Couatl or Kirin or Pegasus can probably use the Elysium humanimal option.With regards to the 5e Aasimar, I wish they were more like their Pathfinder 1st Edition counterparts. The Aasimar in 5e are tied to the angels even though there are different kinds of Celestials. In Pathfinder 1st Edition, you could be a generic Aasimar (one who is unaware of what kind of Celestial sired their bloodline) or you could be an Aasimar from one of 6 specific heritages- Angel, Archon, Azata (PF1's take on 3e's Eladrin), Agathion (PF1's Guardinal), Garuda and Peri (PF1's take on 3e's Asura).
(I will also read up on the PF Aasimar to get a better sense of its traits.)
Heh, even an Ardling who is born into the Material Plane might want to choose to return home to the Astral Plane, and use magic to translate their Material body alive into an Astral though construct.It's not really a choice really. While the first of their kind migrated to the Material Plane from the Beastlands via planar portals, latter generations of Ardlings would have been born on the Material Plane and would have seen it as the native plane. No magic required.