While it is one of the most powerful cards in Commander, WotC decided it is ubiquitous enough that restricting it would be impractical
The best creature type is hard to define, but some metrics can be used to narrow it down: If youre looking for creature types that make good creature-focused (i.e., typal) decks then you probably want goblins, humans, or elves
She's more than 160 decks over at EDHREC.com
The listing implied (without explicitly stating) that these pictures were representative of the collection, like whoever took the pictures just flipped to random pages which just happened to contain multiple cards worth over $100
For $5, you can enjoy a 1-drop red tutor
If youre interested in learning more about a specific prediction, the review is in three parts here, here, and here