Freeze has no encryption or compression features built-in, so you are responsible to prepare the data as you want it to be stored on Glacier before you upload it.

I don't like built-in encryption features in file transfer or backup apps too much, because they are often proprietary and that may make it hard to switch to another client.

As a workflow example, I personally encrypt my archives with gnupg and store them on external hard drives and additionally upload them to Glacier for disaster recovery.