1) how to retrieve the current logged user and its user segment
- Please see attached doc
2) how we change to default display behavior in customize module according to user segment.
This is custom work at this point. What you'd need to do is create tags or categories that correspond to your personalization segments and assign them to your news articles. Then you'd use the appropriate APIs to pull the data back based on your taxonomy and display it in your custom widgets.
You would need to override the default widget's InitializeControls methods and modify the databinding to occur based on the designated filter.
Hope this helps!