1.Can you still only feed on sleeping people or are there new ways to feed on people?
2.How does this power attack feeding thing of the Vamp Lord works.Is it a triggered thing like the kill cams?
3.Can you make bolts for the crossbow(smithing)?
4.Can you sneak as Vampire Lord?
5.Are there any kill cams as a Vampire Lord?

1. You can cast vampire's seduction on people and feed on them standing up. Just don't do it where others can see you, of course.
Spoiler Also there are 'human cattle' to feed on in Volkihar castle.
2. You can earn perks for the vampire lord by either using the mage form and casting the drain life spell or power attacking in melee form and hoping for a kill-cam. They appear to be rare, but I'm not in melee form very much.
3. You can make the crossbows, not entirely sure about the bolts. You have to do some Dawnguard side-quests to be able to do so, however. Oh you can make arrows now too!
4. You cannot, it's similar to werewolf form. You can't access your inventory or use any of your normal shouts/spells.
5. There are kill-cams, they just appear to be rare. See question 2.