Do Enopoly Stores Compete Against Each Other

Simple answer is no. They share at most.
Chances are you cant afford a whole product line from a brand and even if you can afford it doesn't mean it's smart for you to put all eggs in one basket.
Also, we're selling what's selling already and in most cases are aren't bullying other sellers and kicking them off, we all share the platform. There are Hundreds of millions of people with prime accounts, we aren't running out of people who shop online.