First starting out. The PSS's will work for you, BUT once you start getting some track time. The PSS's will get greasy at around the 20 minute if you are really pushing hard. The RE11's will let you go longer and they have a bit more grip. The Mich Cup tires are great, but are $$$. As for tire sizes. A lot of guys run a 18" square set-up.
Read this.
Track Day Best Practices - MUST READ