You can stop someone from scheduling Report Builder files. To do so, go to Admin > Company Settings > Report Builder Reports. Every user (who has access to report builder) will show up here, with the second column showing how many reports have the scheduled and how many in total are available. Click on the edit icon next to it, and change it to 0
You can also have email restrictions, so users cannot send reports outside the company email domains.
Admin > Company Settings > Security > Enforce Email Domain Restrictions
As for the Library, there is no method to disable the usage. This is a shared space where an uploaded workbook can be viewed by any other report builder user in the company. It is similar to sharing it via sharepoint, or dropbox, or googledrive.