The control designer maps all public properties that are exposed by a control and properties of a primitive type like string, int, enum, boolean.
RadControls folder is not presented in installations above Sitefinity 3.2, since all controls are inside Telerik.Web.UI.dll that is located in your bin folder.
You can use LinqDataSource, SiteMapDataSource, XMLDataSource, EntityDataSource, ObjectDataSource etc as a user or custom controls and set their properties from the control designer. The better option is using a ustom or a user controls inside which you bind rad control by using data source controls.
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