Queue priority is dictated by the business case. Calls into a higher priority queue should be handled ahead of calls from other queues. Once within the Queue, calls are handled based on the wait time. Even though it sounds simple enough, it can get complicated because a good ACD (Automatic Call Distributor) has skills for Queues and skills with skill levels for Agents.
So, when does the Skill level get applied? Generally skills will be applied when a call comes into a Queue with multiple agents waiting and available to take the call. Here the Queue Prioritization does not play any role. To summarize, skills based routing is applied to route calls to the correct queue, skills of the individual agent to qualify all the agents who are available to take the call and, skill level to decide which agent should handle a call. Queue Prioritization is applied when agent becomes available with multiple calls waiting in multiple queues. The skills determine if the agent is qualified to handle calls but Queue prioritization dictates the order. The skill level does not play a part here. For an even distribution, the skill levels and the queue priority should be set to the same value so that the longest waiting call or agent is chosen to break the tie.