It has been my understanding that the Imam who joins the couple is under more authority than the law of the land, so one may marry his first wife by law and then the others by the Imam. I have spoken with a couple of Muslims in my country and that is how they do it.
Again with the other my understanding is that each wife lives separate of the other with their own home and comforts. The husband / father visits each house as time permits. That is the way it is done here. This may be largely because the law does not permit plural wives, but maybe in a country that does such as South Africa there is a difference.