You can present yourself nicely without dressing like someone you're not.
It's not necessarily about wearing certain clothes, styles, etc. But you need to make a good impression. You wouldn't go to an interview at a law firm in a hoodie.
Being at a northern school, it is much more laid back, but still, what is wrong with presenting yourself in a put together manner? You need to dress for the occasion. And this is something you actually need to get used to doing to be successful in your future. You're not going to be able to wear hoodies to work forever (though how much fun would that be!).
If you've met a lot of the sisters, they know what you're like outside of recruitment. But recruitment is a special event, and you should treat it as such. Find something nice, but comfortable. Pay attention to fabrics and cuts. Recruitment isn't an every day event. It's a special event. No one wears "recruitment clothes" 365 days a year!
You won't necessarily be judged on what you wear, but if you show up looking sloppy, you will be judged negatively in that you couldn't put forth the extra effort for this special event. While you can be non-sloppy in jeans and a hoodie, it doesn't look as well coordinated as a nicer, put together outfit.
When you're dressed nicely, in clothes that fit and you're comfortable with, you'll feel more confident in yourself and will give a much better impression. If you wore jeans and a hoodie, you'd end up worrying that you didn't dress well enough and comparing yourself to the other rushees.
One thing i'm curious about in your post. Would you be rushing at your current school or the one that you're transferring too? If you're going to rush at your current school knowing that you will be transferring, I think that's more cause for concern than worrying about how to dress
