Swords being power ups isn't news. We know this since swords got a rank (50 skilled swords, 21 great grade swords, 12 supreme grade swords), of course higher quality swords do more damage. That's why Zoro complimented Kitetsu's edge but still called it problem child, as he had to master it.
Yes, Enma is a stronger blade, but still Zoro has to tame it with his own strength and he uses his own Haki with it. Period. Kaido sensing Oden and Big Mom sensing it's no ordinary blade has nothing to do with it. It was said in the manga that the sword inherits the users will. Doesn't mean Enma stored Oden's Haki. Let alone for 20 years.