The Copy/Monitor Tool is handy for helping others start work by acquiring the same Levels and preliminary Grid layout. Then Coordination Review helps us keep these coordinated.
The Tabs in the C/M dialog start from the most "important" or "likely" to use to the "least". That's my perspective about that.
Walls don't C/M very well at this time because Revit forces walls to align via the Wall Centerline Location Line, regardless of Location Line settings applied or in use in either model. What we really "want" for example is to allow RST to C/M RAC walls and map the multi-layered RAC wall to just a RST structural wall type. Doing this breaks down because of the Wall Centerline alignment.
The workaround suggested by Autodesk for the time being is this:
Don't duplicate the walls using C/M feature. Instead, manually draw the structural wall and then use Align to the Location Line of the linked .rvt wall. Once done, you can “Monitor” only feature. By doing so, Revit will remember the offset distance between the center lines of manually drawn walls and the linked wall. it is a pain to have to do it on each pair of walls.
The other gotcha is openings in walls. The overall geometry of the window/door creates the opening in the C/M wall which means it is too large an opening in most cases.