Will it be just like a werewolf where a only your transformation will be attacked or will this automatically make you like a stage 4 vampire that everyone attacks on sight?

They are changing the level 4 vampire now, you won't be attacked anymore. And the Vampire Lord form can be used as much as you want for as long as you want, but if NPCs see you in Lord Form, they will attack you

If they made it that Vampire Lords get attacked whether or not they are in that form would be game breaking. You would not be able to do anything in the game. So no.