Forms are basically styled via the themes and via the CSS on the website they are included in. Your Aivie is already set up so that there are multiple themes in your CI/CD.
Form Minimum: The main part of the styling comes from the CSS of your website. Aivie formats only the form specific elements such as an error message.
Big Text: All form styling comes from Aivie
If you want to leave the styling completely to your website, you can disable the styling completely.