question

Because there are only two procesors with a maximum content of one each, there will never be more than two open transport tasks at a time. And since the dispatcher is set to pass the tasks to First Available the third operator is never needed. To generate more transport tasks at a time, you could place queues with a maximum content > 1 in front of the processors.

When a processor becomes available the connected input objects are checked for items in the order of the connections. As long as there are items are Queue1 they will be transported with priority. To change this you can activate the Pull behaviour on the Input tab of the processor's properties and choose a different Pull strategy. For example, choosing Longest Queue will have the processor pull items from whichever input has more items at the moment.