If you add a goeman draw control with a given set of options, then change the options by setting them on widget, the options are synced to the browser JS but the control doesn't update/options don't change.
EDIT:
This can be forced by doing
dc = GeomanDrawControl(...)
m.add(dc)
....
dc.attr = new value
ctrls = m.controls
m.controls = ()
m.controls = ctrls
The most likely related to needing to force a call to render() or render_leaflet() for the control view to update.