According to Russo's book, it would depend how you look at it. While a boss likely had the final say, he really went out of his way to charactarize Humphreys as the brains and the operator. In terms of leadership, from what I remember, he seemed to suggest that Accardo, Humphreys and Ricca basically ran it as a triumvirate. In his depiction, the question of ultimate power didn't really seem to be an issue.

Makes sense if you think about it. Just like the board of a company.