A. Create a user actor counting 4 channels of video on 4 projectors. Then Create a perhaps up to 20 inputs. Will there be any performance implications.

Not from the User Actor (unless you get *extremely* complex and put hundreds of actors and other User Actors inside, but then any performance issues you'd see would be because of how much you're asking your computer to do; it wouldn't be because all that is in a User Actor). The four channels of video are the only thing in that plan from which I could imagine seeing any sort of performance hit.

@video-architect said:

B. Control the actors from the control panel interface. In which case I presume you can make the ID links inside the user actors themselves> (that there is no need to bring them through to the upper level of the scene editor interface. Im including controls like Movie player 'Visible' on/off and 'Projector' on/off controls with the aim of being able to manage performance if needed.

Yep, you can give Control IDS to actors inside a User Actor/Macro. I would suggest making a Comment actor inside the User Actor where you write down what Control IDS you've used and their purposes. Making documentation now can save you a headache later.