For the RSP, you basically pick the items you want and rank them on a form in order of importance. If you want more than one of a specific item, you fill out a 2nd form and so forth. You submit your form(s) and Disney runs it through their process. I do not know specifically what that process entails, but here is my guess. Let's say for item #1 in the catalog, which has an edition size of 500, they take everyone who ranked it #1 on their list. If there are less than 500, then everyone gets one. If they have some left over, then they move to everyone who ranked it 2nd, and then on down the line. If more than 500 people ranked it #1, then they choose people randomly to get it.
No idea how many tickets are being sold, but in the last 3 years, I have never seen an event sell out like the Friday event did this year (sold out in less than 3 hours). The breakfast and dessert party (which is not offered this year) normally sell out, but normally it takes a couple of weeks to a couple of months to sell out. I am hoping that means that Friday will be much more exclusive considering the price they charged for it. It will be interesting to see if Saturday sells out too.