Quick question. If I take on the vampire lord form after playing with the Dawnguard, are there any perks or powers that I will be unable to obtain?

Nope. Just the two pieces of jewelry.

One more question. When I came out of vampire lord, I could still use the drain life spell. Yet, I don't see it in any of my spells. Is this intentional?

4 pieces of ancient artifact jewelry. +100 Magic and magic regen, +100 health and khajiit claws, bats drain health from enemies, and finally summon 2 gargoyles instead of 1

Whoa, wait, what? I thought DG was essentially "Get practically everything, no drawbacks!" mode, but you seem to know something I dont. If thats true, the paths are much better balanced than I thought.

Do you have more details?

I dont know for sure, as I havnt treid out being a vampire yet/ takeing their side, but if Im not mistaken, the jewelry is like the totems for the werewolf, in that it grants you powers, ans some of the perks require their blessing. I may be wrong in this, again, I dont know. I think you have to join the vampires to get it, though I found/stole a realy cool piece of jewlry from their castle,but I dont know what it is.Also, I think you get bottles of blood/human catle in their castle,and can blockout the sun, so life as a vampire is easier when working for them.

Edit: Nevermind, the perks work w/out jewlry, they are'nt like the werewolf.

That is the details, there are 4 pieces (2 amulets, 2 rings) with heavy bonuses. They are obtained through Vamp side-quests like the DG rune weapons