I'll poke my 2 cents in here. I'm not currently a member of the Orthodox church or clergy of any sort. As has been said, if you want an official response you need to seek out an Orthodox priest and/or bishop. However, I was a catechumen for over a year, and after some time away to look into other churches, have decided I will be going forward with the Orthodox church.
With all that said, I can't presume to answer an unclear question about "authority" in regards to the RCC. I assume you are speaking of a "One True Church" claim. As for the Orthodox, I don't think this claim has ever been made. I've heard the same answer from priests, monks, and bishops in regards to the Orthodox church. They do claim to have the "fullness of the faith" as has been passed down through Tradition. More specifically apostolic succession that can be traced back to the apostles (I have done this myself and you can as well. Google is your friend) as well as the teachings from the early church fathers. The Orthodox do not claim that they are the "One True Church" and that anyone outside the church cannot have the Holy Spirit. Again, as has been told to me from multiple priests, monks, and bishops, the official position is that the Orthodox church knows where the Holy Spirit is but does not presume to say where it isn't.
Hope this is helpful.