Allegedly, QTO automagically quantifies everything that is modeled. If you are using Revit, you have to create schedules for the items to be accounted for. QTO will color code items quantified so you are able to browse the documents are see what has been quantified and what has not.
You will soon discover that architects do not model every item in a building and will insert “cartoons” into the drawing set. The cartoons are 2d drawings used to fill in the blanks. Structural engineers typically only include the significant structural items in the model, stub columns, edge angles, bracing, moment connections are not modeled and could be missed if exclusively relying on a QTO or Revit takeoff.