To separate people I often use the top view and then manually select each character to move them. As far as the number of people, unfortunately, it depends. As more characters are added the slower the program gets. I have put up to 14 P3 people into a scene without a crash, but the program gets very slow. The problem with P4 people is that they take up more memory and their clothes and hair add additionally to that. Also keeping track of characters and their clothing is a pain. I wish after you conformed clothing to a person you could "hide" the clothing from the drop down list and make it unselectable when you click on the character (Let's see do I want to select the shirt's collar or the character's?). To get P4 figures down in size some have suggested setting a character's features using morph targets and then somehow freezing them and removing the individual morphs that created them. I don't, however, remember how to do this.