Most of the controls are described in the web.config => telerik => cms => ToolBoxControls
section you can add or remove controls from there. The remaining controls are programatically added by the Sitefinity modules.
In order to exclude controls for a module you could remove the whole module if you don't need it. In order to achieve this, remove all references in the web.config for this module.
Hope this helps.
the Telerik team