Hi Chris, Very good questions. I'm not a Medium employee but here's what I found out:

- No, there's no priority BUT Medium will show the first tag below your stories. In the past you could see ALL tags.

- The moment you tag 5x you have 5x the chance to become a Top Writer in one of these 5 categories (as long as all are TW tags)

- I would always use : specifc ones and TW tags

Thanks for reading so many stories from me :D Really appreciate your energy.