What do themes in Experience Builder primarily affect?

Themes in Experience Builder primarily affect the visual flow of the site. This aspect is essential because themes dictate how the content is presented to users, influencing elements such as layout, color schemes, fonts, and overall aesthetics. A well-designed theme can significantly enhance user experience by ensuring that the site is visually appealing and aligned with the brand identity.

The focus on themes emphasizes the importance of design in creating engaging and user-friendly experiences. While the functionality of backend systems, integration with third-party applications, and authentication processes for users are crucial for the overall operation and security of a site, they are not directly impacted by the themes set in Experience Builder. Instead, themes are specifically geared towards managing and enhancing the visual appearance and user interface of the site to improve user interaction and satisfaction. Thus, the correct answer highlights the primary role of themes in shaping the visual experience that users engage with.