Sync Settings will be referenced in the later context as "the app".
All data collected by the app is used to enable the app's intended functionality. Consequently, the app reads account information to identify accounts and stores it on the user's device storage for internal use. Information shared with other applications to allow for the desired functionallity contains no sensitive information, but only a key generated by the app to be able to relate actions to the accounts selected by the user. This is never done automatically, but only on the user's interaction.
To the best of the developer's knowledge, no personal (or other) information is sent by the app to the developer or any third party.