Does cPanel backup accounts 1-by-1 or multiple at once?

Hi guys, Let's say we have following scenario. A cPanel Server is using the in-built backup system. There is an additional backup destination, configured as S3 to iDrive. The "Retain Backups in the Default Backup Directory" is disabled. There is one weekly backup configured to run at the end of the week. Two questions: When the server starts backing up accounts as per the configured schedule does it backup them 1-by-1 (ex. create archive, waits for it to upload to S3 destination, deletes it and moves to next one) or it will do a few accounts at once(create a few archives, wait for them to upload to S3, delete them and move to next ones)? The other question is: Is there a timeout limit for the schedule to run (ex. it has to complete by X amount of time) or it will run until it has backed up everything?