Hey male_overhaul,
Thanks for getting in touch. The confirmation email’s formatting can be set up within the MailChimp account itself. If you head in your account to Lists > the list name > Signup forms > General form, you’ll be at the signup form builder. On that screen you can then select which form or related email (such as confirmation emails) to customize, and then proceed to change the contents as desired.
For the second question, what do you mean by the default form info? By default, fields aren’t populated in MailChimp, though you can set Help Text and default values for a particular field to be used within campaigns if someone has an empty value for a field. (You can also change your fields to be required from here.) All of those changes, as well as adding new fields and changing their order, can be made from the form builder screen I mentioned.
For more support regarding the forms in general, rather than specifically getting the WordPress plugin working, I recommend checking out our knowledge base or getting in touch with our general support team via chat or email, all from this page: https://kb.mailchimp.com/chat
Thanks,
Gabe