Chaos itself itsnt necessarily "evil" as a force, just chaotic. Dracula uses it for evil however, and as far as an actual being from AoS goes, "Chaos" is the physical manifestation of the Castle's chaotic flow. The "soul" of the castle, I guess you could say. Upon killing Chaos, Soma effectively destroyed Castlevania.
What I mean is that the Chaotic flow within Castlevania is bound to Dracula and his power. his powers themselves are gained from Walter Bernhard, although the power of dominance may be related to the Crimson Stone.
Or just related to the fact that he dominates all monsters and shit.
by being bound to the chaos within his Castle, Dracula is practically just another creature of the castle. The same way that when the castle materializes, all manner of creatures and monsters arise with it, Dracula also arises, as the master of the castle. It's a perpetual cycle. Some times he is resurrected prematurely by followers, and other times he naturally resurrects within the 100 year cycle. He has no choice, he is trapped in the vicious cycle of reincarnation. Until Julius and the Hakuba priest sealed the castle in another dimension during the eclipse, separating his soul from the chaotic flow which would revive him, and possibly destroying his Crimson stone along with him.
as for Death, wasnt it stated that he isnt exactly the mythological figure that claims the souls of the dead, but just a really powerful necromancer? or "a" Death God? A Shinigami?
On Old Drac vs New Drac, I think we can just settle it like this:
Old Drac was a hands off warlord, directing his troops from his throne, coming to the fray himself only when the last lines of defense are defeated.
New Drac however, seems to be a more hands on "out there in the battlefield" warlord, fighting at the head of his troops, killing anything that gets in his way.
maybe.
At least for their origins it was that way. Mathias carefully planned everything out and had others do his dirty work, only declaring himself once everything has been done,
While Gabriel is really more a victim of circumstance, manipulated by others, but still having done all the dirty work himself, gaining his powers while he was still human, but falling to despair and depression, and once he is forced to sacrifice his humanity to stop a monster he is responsible for unleashing, the loss of his human heart pushes him directly over the edge into the abyss of darkness, where he declares himself.
Mathias is a genius tactician.
Gabriel is a supernaturally powerful warrior.