Please go through this documentation to know about validation settings in Radgrid. Validation
Also take a look at this demo to know more about its working when using EditForms. Grid - Flexible Server-Side Validation
I'm not clear about your requirement. The RadControls which use the HtmlEncode property are RadGrid and RadTreeList, more specifically - all their columns that are inherited from GridBoundColumn\TreeListBoundColumn. Incase you need HtmlEncode you can use a GridBoundColumn with HtmlEncode property set.