The Snap Grid and the Reference Grid fulfill two different purposes and can be manipulated independently in the Plan Defaults dialog.
The default materials for corner boards and quoins can be specified in the Material Defaults section of Default Settings.
By default, a wall’s Main Layer is also its Wall Dimension Layer. You can, however, specify a different Wall Dimension Layer in the Wall Type Definitions dialog.
There are actually two grids in Chief Architect: the Snap Grid and the Reference Grid. The display of both is easily controlled in the General Plan Defaults.