The gist I get is that narcissism decreases with age, which makes sense... Can anyone with good knowledge of stats and that really understands the concepts communicated in the paper ELI5?

What is it saying about the three types of narcissism?

the bbc's layman version (if accurate) was that the behavior "mellows" a bit, or decreases just a little, not enough to change your approach to narcissists. Going completely off memory, the three variations of narcissists were: vindictive, aloof, and neurotic I think.