When does it make sense to use fan-out queuing for high-volume notifications, even with the added complexity?

We're building a new notification system, and it has to deal with millions of events every second. Each one could trigger emails, texts, or push notifications. Right now, we're thinking about two ways to do this. One idea is a single queue where consumers send out all the different notification types. The other way is to use a special fan-out exchange or topic that sends things to separate queues for each type of notification. That second choice seems tougher and more able to grow, but it also means more stuff to set up and keep track of. What have you all seen with fan-out queuing when you're dealing with crazy high volumes? Is it really worth all that extra work, or are there easier ways that work just as good?