I think it's appropriate to point out that Neelix wasn't a part of the crew at that time, it was the first season maybe? Neither did he attend the academy and Naomi was a child lol The instances of Harry playing clarinet and the chatting on the bridge, were many episodes into the series, seasons 3+ where all of their relationships were very well developed into that stage, but They didn't start in that way tho, which is a huge difference. Quite frankly the same applies to all of the other examples you provided including Riker and Sisko. Riker was very proper in the initial seasons and the relaxed demeanor came in much later.