SyncGene lets you undo any synchronization performed. It makes sure you have backups, and gets them back to your cloud sources. The backup data is stored in Google Drive (iCloud/OneDrive will be supported in the upcoming versions). If anything does not go as you wish, simply restore the data from the backup or use your native connected account backup-restore services.
Note: backup will be performed the first time you synchronize your data, then once every month or if you change your configuration - add/remove accounts or change filters.