A vector brush stroke applied to the page remains fully editable and can be modified, while the stroke is selected. On the context toolbar, you can change its stroke width or color; on the Stroke panel you can change its profile, while the Brushes panel lets you swap the brush for another.
For more advanced brush settings you can also use the Edit button on the Brushes panel, with the option to save your brush stroke setting as a new brush preset.
The following settings are available in the Brush dialog's Stroke section: