Question 1: Delta Live Tables (DLT) picks up a location by default in Unity catalog (UC) for storing the data. This location is in the root storage that is configured when you create the metastore. Managed tables, which are the default way to create tables in UC, are stored in this root storage location. If you have specified managed table storage locations at the catalog or schema levels, these will override the root storage location. As for whether it stores the data files in the ADLS location tagged to the meta store, it depends on the cloud provider and storage configuration.
Question 2: Access to data in different catalogs is governed by permissions. Users must have the USE SCHEMA permissions on the schema, and they must have the USE CATALOG permission on its parent catalog. To query a table, users must have the SELECT permission on the table, the USE SCHEMA permission on its parent schema, and the USE CATALOG permission on its parent catalog. Therefore, if the users of business module 2 do not have the necessary permissions for the catalog or schema of business module 1, they would not have access to its data.