We don't know yet, for now I think it is safe to say that Shiryu is the strongest member and the one hyped the most. He was just a bit inferior to a monster like Magellan pre TS but now after 2 years fighting and a DF safe to say he is mad strong.
Burgess is cool and all but he isn't portrayed as the Right hand of BB for now. A guy like Laffite seems more in charge.
We don't know BB organisation for now and I think the number of the fleet doesn't mean much.
For now I put Shiryu but if we learn that someone else is the RH of BB I will modify the thread.