It depends on how many connections you run to the rooms in your house. If it is rather small then you could just use the 4 ports in a router if you have more then you will need a switch. Having a external switch will not have much effect on internet traffic.
The performance is not so much about the equipment you buy for your house but how fast a internet connection you can buy. If you live in the areas that you can only get things like 10mpbs dsl then you are going to have issues sharing with that many people.
I would run at least 1 cable to every room and some rooms it may be beneficial to run more depending on the placement of the jacks. I would run cheap flexible conduit so you can replace the wires or run more if you...