It's been my experience that meeting agendas that feature topics are never as productive as agendas formulated as questions. It's also been my experience that pre-set agendas do not necessarily keep meetings focused, inclusive or productive. Some of the most wasteful meetings I've seen have had detailed agendas with timeframes.
How productive a meeting becomes has everything to do with the quality of questions used to organize the interactions, thinking and engagement. Actually, I would argue that meetings where people build the agenda as they go in meetings can be far more productive than unilaterally imposed agendas.