For the most part, in the comics Captain America's identity was a loose secret. He wore his hood/mask costume and didn't use his real name. Iron Man bounced back and forth between been open and lying about his identity, if it wasn't someone else in the suit. Hulk's identity wasn't known to the general public either, but it wasn't a secret. Of course, in the MCU, everybody knows their identities now. Even if they didn't know before, after SHIELD's files were dumped to the internet, it's just a google search away.
Originally Carol wore one of those little, pointless domino masks as Ms Marvel, something that's been discarded. And a lot of people in the super world knew who she was anyway. I doubt they will be making much of an attempt to hide her identity any more than any of the other Avengers. Maybe not go out of the way to announce it like Tony did, but not try to keep it secret either.
It's interesting to note that the art they showed for Black Panther is very close to his usual comic book appearance, which is a full body suit and face mask. Something that's kind of a no-go for movies and television usually. It's considered a bad idea to cover up an actor's face because it make it harder for them to express and emote. It's easier to get away with in comics because they are a partly written form of storytelling.