Both approaches seem fine so I guess you could take the one you are more comfortable with. It is your personal decision whether you should start with the UI of the application or its models and view models.
Personally, though I am not familiar with the "Catel
" Framework in details, I believe it will be more convenient to start with setting up the MVVM Framework and eventually you can add the Telerik references at any time. On the other hand, initially setting up your application as Telerik UI for WPF project would give you the possibility to automatically add the Themes for your controls and the references needed.
As the "Catel
" Framework is a third party software, we cannot be sure of the exact result so I suggest you contact us in case you experience any issues during the setup.
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items