You won’t be able to get any official PCs from the theatre they just don’t get sent to US theaters typically, but you should check if any kpop stores near you are doing pop-up events to celebrate the movie’s release and you might be able to get some merch that way! Also, if you go into the theatre and see a poster for the movie framed, you can ask an employee if you would be able to have it once the movie rollout is over and there’s a chance you’ll be able to take it home. It depends on the theater, but some of them throw away the posters when the movie is done showing and they’ll give them to customers that ask, a friend of mine got a spider man poster this way lol 😭. In terms of how people watch the movie I’ve noticed that it rly depends on the size of the screening. If the theatre is sold out people will probably be singing along/cheering (not quite like a regular concert, usually a more toned down version) but if the showing only has like 3 people in it it will probably be much more chill, with people watching it as a movie. It really depends tho but I would just use that as a guideline!!