The tablet applet makes it possible to change the available profiles on the fly. Furthermore you can change the pad rotation and switch between absolute/relative mode of the stylus/eraser regardless of the current profile settings.
It is not necessary to add the plasmoid for this module to work. The default profile will be activated by the tablet daemon as soon as it detects your tablet even if the plasmoid is not used. The plasmoid is just a visual helper to switch easily between the profiles.