Hi,
rubber balls might actually be useful in some (admittedly rare) circumstances: if you are way everyone else, the rubber ball might force the leader to be rescued, and resulting in other karts overtaking the leader. A kart ahead of the leader will then get eliminated instead of you. Difficult to time admittedly

But also the rubber ball might hit other karts on its way as well.
Different paths: again, might be useful (when playing with many karts, the main path might be too crowded) but risky. So I would recommend people to follow the leader (hey, what's the name of the mode again?), but no reason to restrict them to that.
Cheers,
Joerg