The Snap Grid and the Reference Grid fulfill two different purposes and can be manipulated independently in the Plan Defaults dialog.
The Corner Trim category listed in Default Settings allows you to access both the Corner Board and Quoins defaults, which include the materials.
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.