1) Could you please confirm if the Pega Data Mover Utility supports data migration from on-premises to cloud ?
Pega Data Mover can be used for on premise to cloud migrations, especially if the customer is on DB2/ZOS on premise. If not, AWS DMS is probably a better option to move to Pega Cloud.
2) Can it supports encryption at rest/transit during the data migration ?
3) Also, how long it will take to transfer 16TB of data on network ?
16 TB is a very large DB. You will need a strategy to unload data in parallel to reduce the downtime. Once you have a migration strategy in place for the database under consideration, please do a trial migration to derive the actual migration time and application downtime.