A queue can be used to guarantee that all events get passed to projectors in the right order. If you want a projector to handle events in a queue then simply add the Illuminate\Contracts\Queue\ShouldQueue interface to your projector just like you would a Job.
A useful rule of thumb is that if your projectors aren't producing data that is consumed in the same request as the events are fired, you should let your projector implement Illuminate\Contracts\Queue\ShouldQueue.
You can set the name of the queue connection in the queue key of the event-sourcing config file. You should make sure that the queue will process only one job at a time.
In a local environment, where events have a very low chance of getting fired concurrently, it's probably ok to just use the sync driver.