Why do all of Vlad's vampires suddenly turn Always Chaotic Evil and claim that all of humanity will be their enemies? Because they remember how they reacted to seeing Vlad as a vampire. Yes, Vlad was able to survive it and tell them off, but only because they tried to set him on fire instead of staking him or robbing him of shelter from the sunlight. Rather than take their chances trying to do that to the rest of humanity, they'd rather just be the monsters they're seen as.
There's also the fact that while Vlad fought his bloodlust with Heroic Willpower every step of the way, his people just immediately started gobbling up Turks, so they probably succumbed to it pretty quickly.
Also, consider the very circumstances of the respective initial vampirizations. Vlad became a vampire purely to achieve the power necessary to protect his family and his kingdom. They explicitly became vampires to get their revenge on those that had hurt them. Something born of vengeance isn't going to be as good as something born of the desire to protect others.
Vlad originally got his vampire powers for 3 days because that deal happened on Easter Monday. Jesus came back from the dead on the third day since his crucifixion.
Vlad's moniker of "Dracula" means "son of the dragon". His vampiric sire lives in a foul, gloomy cave atop a barren mountain peak ... which is the classic abode for actual dragons in folklore.
The fact that the Master Vampire can speak the same language as Vlad despite being trapped in a cave for eternity can be explained away by him being a former Roman emperor (according to the script). Romanian is descended from Vulgar Latin, so Vlad is probably able to pick up a lot of things the Master says, even if he doesn't understand him completely. Alternatively, being a Latin speaker allows the Master to easily pick up Romanian via listening to his surroundings with his super sense.
