backing up my backups...what to backup?
If you only want the latest backup, then yes - it is enough to just dump the latest folder to your extra backup drive.

Each of those folders (the dates) contains the full backup as it looks on that day.

Note that Time Machines saves space on the drive by using hard links to "deduplicate" the backup. This means that if you want to copy multiple dates to your extra backup drive, you'll probably want to handle hard links - otherwise the size of the backup will normally double for two days, triple for three days, etc.

Remember: If you're only copying the latest date folder to your extra backup, you will not be able to restore files that were recently deleted, but stored in the folders representing earlier dates.