is it all about looks?

No, it isn't all about looks.
Definitely rush! There will be some superficial houses who will drop you early on, but the majority of houses here want someone they can connect with and bond with, not just another pretty face.
The most important thing is to be confident. Rock your outfit, have killer hair and makeup, and know that you're beautiful. Because if you are insecure, we can tell, and then it's awkward. But if you strut into that house (respectfully and without attitude lol) and have a great conversation with the sisters, you should be OK.
Basically, rush. Don't let your weight stop you from doing anything you want to do. :)

I'm going to stress that nobody answer that question. It's a very fair question but I honestly think you should be able to go into rush with an open mind and not think negatively of any of the houses. Their opinion of superficial houses could be different than yours, but let yourself make that call without going in with a set opinion. Make the most out of rush and have a great time :)