Check out this page, it has a lot of login screens. As you can see there, there are many options, including the options you provided. I wouldn't dare to say there is a best practice, given there are tons of options you could consider. What I would say, though, is to consider these things:
- Is a login/signup really neccessary? Is there nothing the user could do without signing up? Is it not possible to store data offline? Sometimes you can't get around it, but people have to create yet another account.
- Keep your design spacious. My fingers are quite thick, and so, like many other people, I don't have small fingers like a 12 year-old. Screens like these can get cluttered really fast, and it's annoying when you can't see what you're pressing.
You can't really go wrong with the designs you provided. :-)