The only way to have uncontrollable sims in Sims 3 is by sending them into a rabbithole or by accepting the opportunity to send parents on a vacation (I wouldn't recommend that one, because it's very buggy and can break your game). And teens you can send to boarding school. Of course you can send them to one of the WA worlds or Oasis Landing (ITF); the sims left home will become uncontrollable, you'll indeed always follow the travelling sim though. When you return in WA's case time stood still, where in Oasis Landing it's possible to keep aging enabled.
That being said, sims in 3 are perfectly capable of taking care of themselves. So you can just follow one sim if you wish and leave the others to their own devices. When something important happens (birth, fire) the camera will automatically switch to them. Or you get notifications (for example when they're invited to a party).
