Definitely. You can make any signup form associated to a mailing list as default. Open the Contacts tab and click Forms. You will get the signup form list view with the associated mailing list mentioned. Hover over any form and click ...
You can create a replica of your signup form using the clone option. Open the Contacts tab and click Forms. You will get the signup form list view. Hover over any form and click Clone icon to complete the action.
A thank you page is a site page that a contact gets redirected to on filling a signup form. Zoho Campaigns provides a signup thank you page and confirmation thank you page.