They are really just deciding where they want to live beforehand so that when they get down there, and they are asked that, they will have an answer. Wellness is for those under 21, and just means that there is to be NO alcohol in that apartment lest they all get termed for it if there is some. You can be in wellness if you're over 21, but it can be risky because if a roommate decides to bring alcohol in and you don't turn them in, you get blamed and termed too since you're over 21. Non wellness can have alcohol in the apartment, but is only for those 21+
The different housing complexes are vista(oldest and has a reputation for being loud and lots of parties, also the cheapest) patterson(newest, quietest, and pretty calm, more expensive) and Chatham(in the middle of vista and Patterson, I lived in Chatham and it was pretty quiet though)
And then people usually decide ahead of time how many roommates they want. You always share a room, but you can have 1-7 roommates, so 1-4 bedroom apartments. 3 and 4 bedrooms are cheaper rent since there is more people, but more chances for drama IMO. 1 and 2 bedrooms are more expensive but less people to deal with. You can also sometimes request which floor you want to be on, usually the top two have balconies, and the bottom floor has a porch sort of thing. I lived in a 2 bedroom on the bottom floor at Chatham and loved it! I lived there for 9 months and kept all but my own roommate the whole time(she got extended but opted to go home instead so she didn't lose her scholarship)