Hi i was wondering myself now that i fully became Vampire lord if i can can turn again into werewolf asking to Aela the Huntress (my wife) to unlock WW perks. But if i do this, can i turn back into vampire Lord and have all my already unlocked perks?

And there is a way to turn into Vampire again without Harkon alive?

if u didnt cure serana she can change u back just like aela does and yes ull keep the perks

I have a question relating to this topic.

Can I be neither? Right now I'm doing the vampire side of Dawnguard for the first time, and when I'm done, can I choose to not become either one?