Filevault for all volumes
When you adding APFS container, you should be able to use APFS (Encrypted)



I found that after added, it will be shown as 'APFS (Encrypted)' in Disk Utility.app. In diskutil list, no encryption status is metioned.

I didn't find out how to encrypt / unencrypt an existing APFS volume in Disk Utility.app. Maybe some diskutil command will do it.