I want to know what feature nbu supprt when destination is cloud . suc as compression, encyption, deduplication etc
Also i would like to know what is difference between the encryption enable from the policy and encryption enable during cloude storage creation.
Refer to this section in the NBU Cloud Admin manual:
About data encryption for cloud storage
You will see in this section that KMS encryption is used for cloud storage.
Client-based encryption in the policy is covered in See the NetBackup Security and Encryption Guide:
You will see that it requires configuration on each client individually.
You can also read up about different security models in Chapter 2 of the Security and Encryption Guide.