When I do a 2D drawing on the top view and the scene contain 3D content, it regularly happens that the points are not aligned. How to re(align) this points without change the top view draw ? Or, how to do a draw on a view with all the points on the same alignment ?
Also, when you are not working on the active CPlane and want to prevent snapping to other geometry, you can use the Tab key (possibly in combination with the Shift key) to lock the direction before snapping to reference geometry. Or snap to reference geometry with the Ctrl key active and then snap to your new geometry in a different viewport.
-wim