"If you’ve been using microformats or RDFa to mark up your Google Rich Snippets, sorry, you backed the wrong horse."

I think that's supposed to be a joke, but it just comes off as insulting instead.

Well, if you used microdata, you have an easy migration path, and if you used some other syntax, you don't. You can call that whatever you like, but it doesn't change the facts.

Can you use this microdata with your own CSS/HTML markup or you can't include your own classes ? i.e. your formats must look identical to these ?

You can fit microdata into any markup. It's just some HTML attributes, plus the values that are already visible on your page.