I became a Vampire Lord right away but I fortunately made a save just before this decision so I can go back. However, if I decide to continue on as a Vampire Lord will I miss out on anything cool from the Dawnguard? I read somewhere on a forum that there is a guy that has a high probability of carrying Steel Boots with the Muffle Enchant at Dawnguard Castle. This is the only enchant I have not been able to add to my list of learned enchants so will he not be there now that I became a Vampire Lord? This is the main thing I am after unless there is some other insanely cool items I am unaware of.

Also, since I am a level 81 character what are the best places to go or way to go about boosting those perk trees for both Werewolves and Vampires? I don't want to be making transformations only to get instantly creamed by enemies since they are leveled to my character.

If you are a Vampire Lord the Dawnguard will not talk to you. They're kind of [censored]s about it.