The default mode is TrackMode.None, which means you cannot draw or edit features at the client side. By setting the mode to TrackMode.Point, TrackMode.Line, TrackMode.Polygon etc., you can then add points, lines or polygons to the FeatureOverlay. Setting the mode to TrackMode.Edit, you can edit the shapes at the client side.
The EditSettings object contains four options: IsDraggable, IsReshapable, IsRotatable, IsResizable. By default, all of them are set to true. This means you can drag, reshape, rotate and resize shapes when you are in edit mode. If you set any of these options to false, you prohibit that functionality.