About the 3 version, so GAL’s Project is simply “not canon”, and the other 2 version are connected, so they’re the “official ones” (like “Life Shaping Handbook”, based upon “Windriders of the Jagged Cliffs”).
The 3rd edition levels seems more convincing, powerwise. Since those undeads exists for thousand of years, it’s normal if they’re epic.
Confronting their 2E with their 3E stats…
Why Qwith (a necromancer/psionicist) became only an arcane caster?
And with Gretch as a morg (you “took a third option” since fluff and stats were discordant about the fact that he was a Kaisharga or a Zhen?)… does it mean that “someone” transformed him in an undead?
And since those 4 rulers are in a “double stalemate” with each other and also with the bugdead nations, I think that even the S’thag zagath emperor, the Successor, will be quite poweful.