Traffic Shaping: Question

[ermannobonfazi]

Hello, I'm new to OPNSense. Coming from another solution where I was using QoS. In OPN seems a little different.
My question is about the concept of Pipe. Assuming I want to create priority and "reserved" bandwidth for a VoIP Class but also I want this bandwidth to be avaiable for the other traffic when there is no Voip traffic. Should I create a Pipe or Queues? Reading the documentation on the web site seems that if a pipe is created you need to create a pipe for the remaining traffic too, that let me deduct that this will reduce the amount of traffic even if the pipe is not used. Am I wrong? What 's the best option to achieve my scenario?