Users with Business Premium License can see the content of labeled encrypted files?

Dears,

In my company we have different users with different licenses. Some have Microsoft Business Premium, others have Enterprise E5

In the organization, we have a collection of different things that we want to apply sentitivity labels:

1 - Files (Word, excel, powerPoint, etc..) which exist in a One Drive place

2 - Files (Word, excel, powerPoint, etc..) which exist in Azure Shared file drive 

3- Files (Word, excel, powerPoint, etc..) which exist in AWS Shares Drives

4- Files (Word, excel, powerPoint, etc..) which exist in AWS S3 buckets

Questions:

1 - Is it possible to apply sensitivity labels directly to the files which exist in all this different shared drives? or AWS is not possible?

2 - Please note, we want the labels to be sticked to the files to classify them but as well to encrypt those files so that only allowed people can decrypt them and see its content

3 - Some users have business licenses and others have enterprise E5 licenses. I know that the ones with enterprise licence , if they have permissions they will be able to see the content of the files. But what about the users which have business premium licenses will the license affect their capability to see the content of the file because they are not able to decrypt it ?

Thanks, Pedro