Hello Preet,
The RadToolTip's default behavior when you have not explicitly set sizes is to autosize according to its content.
Would you please test its behavior without setting sizes and in case it is not what you need, please clarify what exactly you want to achieve? It will be best if you open a new support ticket and send some screenshots along with a detailed explanation and a sample working project.
All the best,
Svetlina
the Telerik team