Hello Clark Farabaugh,
Thank you for contacting us. Regarding your questions:
We have not observed incompatibility when using different third party controls. However, we cannot control their appearance and they will look inconsistent when using our themes. So, in order to achieve consistent and professional looking application we suggest using Telerik
controls entirely. Please, tell us which controls do you need for your application. We will appreciate this information and it will help us to shape our suite better.
Our controls rely on the standard sizing mechanism build in MS Windows and glitches may appear when using Windows XP. Nevertheless, such cases are rare and our support is ready to assist when issues appear.
I hope this helps. If you need any further information please do not hesitate to write us.
All the best,
the Telerik team