Thanks for using Syncfusion product.
1. Customizing schedule header and day header.
As of now your requirement can be achieved by overriding the default template of schedule header and day header. We have prepared a sample for the same and please find the sample in the below link.
Sample Link: Schedule_WPF_120618
2. Margin around appointment.
As of now we don’t have any support to reduce the margin around the appointment. We have provided appointments with margin to show the appointment selection.