Hi there! I'm studying at St A's and just going into my 2nd year. I also shared a room last year so I'll try and give a brief insight to that as well
St A's definitely has a reputation for being snobby but in my experience, it hasn't been anything like people made it out to be. I think a lot of it stems from the fact that it's student population is very international (and international students are typically quite well-off). The fact that Prince William and Kate Middleton went there has also gone a long way in creating the impression that it's a very posh place but really, it's not. It's more 'prestigious' than anything else. I was worried about the exact same thing (and having a read of other threads on here, it's not an uncommon thing) but don't worry! If you end up coming to St A's - or wherever you decide on going to uni - you will definitely be able to find your people. One of the best things about St A's is the fact that it's so international, so you end up crossing paths with so many people, often from different backgrounds, who you'd otherwise never have met.
It's funny you use the word bubble as well. St A's is actually known as 'the bubble' to students because, well, it really is one
But in a good way! It's a very safe and friendly place to study. In terms of friendliness, I found most people (especially in freshers' week and beyond when everyone is desperate to make a few friends) really nice! Because the town is quite small, you tend to find yourself bumping into people on your way to lectures, tutorials or back to your accommodation so people become familiar pretty quickly. What I've also found as well is that the vast majority of people who go to St A's seem to really care about the subject they study (which is sort of a prerequisite now I think about it, you have to to get in!) which is really refreshing. It makes a real difference from school for sure.
On the roommate thing: I had a mixed experience. I signed up for a shared room thinking I would end up in the halls in town (think St Salvators or Mackintosh) and I ended up in DRA which is the accommodation furthest away from town. So, that's something to consider. It's also only slightly cheaper price wise. I know people who had a great experience with their roommate who ended up becoming really good friends but sometimes you just don't gel which is okay! If I could go back, I'd definitely have chosen a single room because I realise now how much I value my own space to switch off - but that's just me. St A's is odd in that it even
has shared rooms, but if you want the experience I'd say go for it! They do try to match you up with a short quiz while you're filling in your accommodation form (like what time you wake up/go to sleep, hobbies etc) but if you do decide to have a roommate, I'd definitely advise setting some kind of ground rules with them from the off so you're on the same page
Hope this helps, I'm happy to answer any more questions!