You can look over the Shading Surfaces section of the Input/Output Reference for more info, but to give short answers to your questions:

• Yes, you do need to add a WindowProperty:ShadingControl object to your model in order to implement a control strategy.

NOTE: This object DOES NOT interact with the FenestrationSurface:Detailed object to model complex windows. You can define your window using individual glazing and gas material layers in a normal Construction object, model simple windows, or use EMS variables to control shades if you must keep the complex windows.

• Two key inputs used by the window shading control object is the name of the window construction using variable shading and the material of that variable shading. You DO NOT need to sketch a shading surface.

NOTE: The shading control will be applied to ALL windows with the construction you enter. If you only want want to implement shading control on specific windows, or look at different shading control strategies (setpoints, schedules, blind placement, etc.) across multiple windows in the same simulation, you will need to create multiple window constructions in your model.

• Yes, you should see different results based on shading device placement and type. The shading device will still block direct light penetration through windows depending upon transmittance, but exterior devices will block solar radiation gains on the exterior window surface while interior devices will not. Also, there are some subtle differences between shades / blinds / and screens in EnergyPlus. For example, shades are perfect diffusers while reflective properties of blinds vary according to solar angle of incidence. The impacts these options have will depend upon your model (building use, location, operation schedule, etc.), so you'll have to test them out to see what impacts they have.