no you cant be both, if you want to be a vampire and your a werewolf the head vampire will give you a choice of want you want to be.

During the questline the head vampire makes you choose.

Yes you can be both of those. But not on the same save.

Symbiote wrote Yes you can be both of those. But not on the same save.

You can be both of them in the same save, if you want to be a vampire go talk with Serana and if you want to be a werewolf go talk to Aela from the companions.

What I don't understand is when you choose to be a Vampire from Serena at the end do you get to do any type of questline?
Also, is there any thing else to do in the Dawnguard questline besides the main and crossbow blueprints?

There is a glitch so that you can be a vampire and use the Ring of Hircine to still have werewolf transformations.

yes, you absolutely can be both with a game modded with console commands. join and become a werewolf so you can do the quests, then go become a vampire lord or just a vampire (get rid of the actual werewolf power). then use the console to give yourelf the werewolf transformation power. once you have that, you can become a vampire/keep vampire lord powers without losing the werewolf power. you can switch between the two.

just having the beast form power when you become a vampire lord, won't remove it. you have to actually acively be a vampire and only then will the dialogue appear. you won't be able to use hircine's ring, though. but you have to do it in that order. getting rid of werewolf will remove the power otherwise.