Which method helps in updating Google Groups efficiently after the initial sync?

Utilizing the Groups Settings API for simultaneous updates is the most effective method for keeping Google Groups updated after the initial synchronization. The Groups Settings API allows administrators to programmatically manage settings and configurations of Google Groups, enabling bulk or simultaneous updates. This API is particularly useful when there are numerous changes to be made across multiple groups, as it enhances efficiency and reduces the potential for errors that could be introduced through manual updating methods or the user interface.

By using the Groups Settings API, organizations can automate the management of group settings, ensuring that modifications such as membership changes, group visibility, and permissions are applied consistently and quickly. This automation is essential for maintaining the accuracy and relevance of group configurations in larger environments, where manual updates could become cumbersome and time-consuming.

Other options may not provide the same level of efficiency. For example, while the Domain Shared Contacts API allows for creating shared contacts, it does not directly manage group updates. Performing bulk updates through the G Suite Admin's user interface can be time-consuming and prone to human error, especially with a large number of groups. Employing the Google Cloud Directory Sync tool again would typically be aimed at synchronizing user accounts with the directory but may not effectively handle the nuanced settings of individual groups after the initial sync.