You can remove scrollbars for inner levels using this property:
The RadGridView control does not support many to many relation hierarchy with suitable UI presentation out of the box. You can setup manually many to many relation adding GridViewTemplate for second and third level with the same columns schema and same DataSources, but the result will be more complex and this can decrease the performance of your application.
You can try to use our RadTreeView control to present your data.
I hope this information is useful. Let me know if you need further assistance.
the Telerik team