The current state of consensus protocol on xDAI

Hi All :wave:
I’m going over the xDAI docs, trying to learn more about the consensus protocol now and looking forward. I must say that I was left a bit confused. Partially due to an overwhelming amount of terminology, I am not sure I understand how consensus works on xDAI at the moment.

How is the current validator set determined? What should I do if I want to become a validator now (Theoretically)? Do I need to ask permission and be voted in?

What consensus protocol do validators use at the moment?

To help out with the terminology, out of the following, what is currently in place, and what is planned for the near and far future (POA, POSDAO, AuRa, HBBFT)