Currently the files can only be deleted from the backup storage tab via software GUI. This might change in the future.

To delete everything that was backed up by a certain machine follow this guide: https://mspbackups.com/Admin/Help.aspx?c=Contents%2Fhelp_drop_users.html

By the "folder name" I presume you're referring to the backup prefix. You can also do that by manually typing it. Note that all backups from the old folder need to be transferred to the new one manually after that. Or you can start from scratch.

1. It won't. You can go to Users->Users page and click on the red cross for a specific user which has a computer configured to. By clicking the red cross you will a pop-up that will show a selection of what to delete (all/specific computer/delete nothing, but the user reference). Deleting from Capacity report won't delete data in the cloud.

2. Folders in the cloud depend on users.
Go to Users->Users and click on the user icon on the lefthand side of the screen and you will see its user-id in a pop-up. In the bucket, it will be like %bucketname%\MBS-%user-id%

Thanks Anton. That is the info I was looking for.