Time Machine backup constantly transferring 30gb+
I  use the application BackupLoupe to examine my Time Machine Backups. This enables me to see what is in each backup and then set exclusions as appropriate to meet my needs.

The biggest exclusion is the folder my virtual machines are stored in. I never allow Time Machine to backup my VM's.

System Preferences > Time Machine > Options... > Exclude these items from backups:

Note: I have no affiliation with soma-zone the developer of BackupLoupe.