The following exercise can be done with either the Pen tool, the Brushstroke tool, or the Pencil tool.
Click the Brushstroke tool. On the Object Type toolbar select the 15 pt Round Brush type and create an outline of an image. Click your move tool and deselect. So far so good.
Note that on the Object Type toolbar, the Brushstroke says “15 pt Round”, but the Stroke (a very different tool, and to the left of the Brushstroke on the toolbar) stays at “1”. This is very important to watch.
Select the outline again. Choose a different Brushstroke (5 pt Oval) from the Object type toolbar, and the look how the outline changes appearance. So far so good.
Look on the Object Type Toolbar again. The weight of the Stroke stays at 1. This confused the hell out of me until recently because I had assumed, “A stroke weight is a stroke weight, and they’re all connected. Somehow.” I’ve decided that it’s best to think of the Stroke weight as an afterthought, a fine tuner for creating a Brushstroke to save in your library, then to be avoided altogether afterwards.
For example, Charcoal comes as a default Brushstroke in 1 pt. weight, and that’s it. So if you need to adjust the stroke weight, then go to the Stroke menu. However, I strongly suggest that if you do use the Stroke menu to adjust the weight, you then save that Charcoal Brushstroke with the adjusted weight in your Brushstroke library, and then discontinue using the Stroke menu. To use the Brushstroke in conjunction with the Stroke weight as standard practice without saving the Brushstroke itself for later use is highly volatile, confusing, and very frustrating.
Conclusion: If you have a particular Brushstroke style you need to use, either use the defaults that come with Illy and ignore the Stroke weight, or use the Stroke weight to create a new Brushstroke and store it in your library for future use.
Stroke and Brushstroke are interdependent of each other, and probably shouldn’t be used together as standard practice. I hope this wasn’t obvious to everyone else already, and that I helped you out today. : )