I know that this might have been answered in another post and the last post is a bit old, but it's still unanswered so...
First, the Properties windows for brush DON'T allow to change the features of the Brush tool! If you want pixels/Type/Scales/Cap/Join option, you can only the pen tool.
To change the Brush tool options, everything is located at the bottom of the tool window (where you select the Brush tool).
Those options include :
Draw Object, Lock Fill, Brush Mode, Brush Size, Brush Shape, Use Pressure and Use Tilt
Draw Object, Lock Fill, Use Pressure and Use Tilt are "activate" options where you use them or not.
Brush Mode, Brush Size and Brush Shape are drop down button that let you choose different options.
