There is a way to do everything asked above. There is a Freehand Mode and a Shape Mode, as I understand it.
- If we click on the Pen or Highlighter Tool Buttons then drawing commences in Freehand Mode.
- If we click on the Shapes Tool Button then drawing commences in Shape Mode.
- If we work in Freehand and our shape is unintentionally converted to a fixed shape pressing Undo/Ctrl-Z backs up one move and we get the freehand shape again.
Therefore a simple click on the right Tool Button before starting to draw is all it takes.
If we start to draw directly and notice that the Mode is not the one we desire, then we can just Undo and click the right Tool Button.