What? How do you portrait , as you say, "absolute power" without killing hundreds of thousands of soldiers?How are they different? The only difference I see is hundreds of thousands of soldiers not dying, and Ainz not having to act badass.
That aside - the difference is:
One is rightful and just, the other is not - for the people in that area/time.
If a prince murdered a king, he wouldn't succeed the throne without any issues.
If the king died on the battlefield against some external threat however, no one would question the succession.
He doesn't want to be seen as a tyrant by the common folk..it doesn't do him any good, it's certainly not beneficial.
as for the wiki quote...
? I don't know what you are trying to point out?
That's what declaring independence is..
Episode 10:
The official message is that the Empire recognizes the land near E-Rantel as territory owned by Ains Ool Gown and the Kingdom should return that land to it's original owner and will ally themselves with the Sorcerer King Gown to liberate him from unrighteous rule. (they are basically pushing his claim)
declaring independence is a declaration of war against the party that is currently ruling over the would be independent country.