In more than two decades as a BGO, I've seen zero evidence that participation in military ECAs makes any difference in an application. Many schools don't offer them. Even when they do, many students don't participate for all sorts of reasons.
Just like any other college, students at USNA bring all sorts of talents. Some are actors, singers or musicians. Some worked on their school newspaper or yearbook. Others were active in the science club or language club or service club. Some in Scouting. Others in church/religious activities. Some in Big Brother/Big Sister. Some volunteer for various charities. Some are active in political organizations or supporting political candidates. There is no "right" activity . . . and really no "wrong" activity (other than obvious ones).
Choose ECAs that appeal to you.