There's not really any reason to play separate games with each race. Actually, once all the dungeons open up, the way it's structured, the only difference starting a new game would make is making those original dungeons easier. I think that if you wanted to mess around with a variety of characters, the best thing would be to create multiple characters and alternate them so that they all stay at about the same strength. -- Of course that will make them all considerably weaker and have you replaying levels more before you can beat the last bosses.
Super Mario 35: It would probably be best to base your questions on the things we've described already. Asking about random random features from other games, just complicates things. It's like me asking if Mario gets a better sword in Mario RPG even though no one ever mentioned swords in the first place.