Will the sync create duplicates in the other system?

No, the system does not create duplicates. 

• For the sync with Case Management / CRM tools you have the option at sync time to link the DV matter to the existing matter in the other system and update the records. Then after the first sync DecisionVault will update the records in the other system.
• For the sync with Draft Platforms DecisionVault will create objects in the other system. Then after the first sync DecisionVault will update the records in the other system.