Posts pertaining to non-corporeal creatures.
>mainly being able to classify them clearly.
A general classification may be difficult. The term "non-corporeal" is usually used in a descriptive sense rather than in a narrow technical sense, especially in our documentation. We have a narrow technical sense in the actual code, but there's no guarantee that any individual mention of "non-corporeal-ness" adheres to that technical definition.
That said, the technical version of "non-corporeal" is that the creature has no body parts that are corporeal and has several body parts which are specifically marked as non-corporeal. A creature that has no body parts at all (as per certain elementals) is not considered non-corporeal. The major difference between being non-corporeal and having no body parts (for standard combat purposes) is that the former can be affected by abilities and spells like SMITE and 704, while the latter cannot. There is also special messaging for non-corporeal undead but not for non-corporeal living or no-body-part creatures. Neither non-corporeal nor no-body-part creatures can be wounded (or crit-killed, which is based on wounding). And for completeness, certain corporeal creatures cannot be crit-killed, but may be wounded.
>Do they all (instead of many) evaporate quickly?
Evaporating quickly isn't part-and-parcel of non-corporealness. I'd guess that at least 90% do evaporate quickly, but I can think of a few that don't. It is a per-creature setting.
>Are they all immune to critical kill shots (instead of usually)?
This is part-and-parcel of non-corporealness, yes. Note that this refers to standard melee, ranged, bolt, unarmed, and maneuver combat -- spells and unique damage systems may have their own rules.