How do the brackets work?

Like, can I check each card in my deck to see what its bracket level is somewhere? And then do I just take the average of those values to determine the bracket my deck is in? I was reading the article, and aside from the game changer limit It feels really broad. I don't really understand it aside from "I've played this deck enough to get a sense for it's bracket" but that seems really arbitrary.

:EDIT: Y'all I read the article. That's WHY I'm confused. It just seems like kind of generic information. I just was hoping it would be a bit more codified. No need to be so aggressive.