Thanks for the comments. I think explaining why you’d be best for a role should be framed by the responses you get when you find out more about the hiring manager and their situation. (This is outlined in #3)

In short, you should use SPIN selling techniques, that is, figuring out a person’s exact situation, problem, and implication, before telling that person why you would be the best person for that position.

How would I know how to frame that without knowing the hiring manager’s reasons for the position?

I can’t tell from the web site. I can’t tell from the job description. I’d have to get into the manager’s mind about what is best for the position.

For example, the job description can say that I need 27 competencies, but the manager may take those as a given and have the most important hiring criteria as being the “fit” within the team.

How would I know that?

Unless the manager is open during the interview, it’s a crap shoot.

In those cases, I’d go with my personal brand. At least it would show my strengths and I’d have to hope it matches the reasons for being the best in the position.