[dnanian]

"Drive at the top" is not a documented or guaranteed situation. If you want to check the startup drive, use the "About This Mac" panel in the Apple menu.

Your backups are in the log in Window > Show Log (for manual backups) or, Window > Scheduled Copies (for scheduled copies, select the schedule and click Show Log).

You want to use "Backup - all files" with "Smart Update" in about 99.9% of cases to do a backup.