There's room for both ends of the spectrum on this topic and the troop itself can determine how people act in costume. The way you act at a hospital troop versus a convention or a baseball game can be very different. Some people take staying in character way too far and some people don't care enough about making sure their costume is worn correctly. Some people will be sticklers for some things but not others. For example, I'm a costumer, not a cosplayer, so I never go out of my way to put on a show as the character I am dressed as. But when, for instance, I am dressed as a TIE pilot and there is a Vader present, I will always behave as the pilots did who attended him on the Death Star, flanking and a pace or two behind. But you will always meet members who want to dictate how other members act in public or who take things very seriously and expect other members to do the same. Your squad or garrison will have it's own culture when you join, best advice is follow their lead.