For Sharing a CSV file containing PII data with another user who should not have access to PII data elements:

• You can use Databricks' Unity Catalog to manage and govern access to data. Unity Catalog allows you to define fine-grained access controls at the column level, ensuring that users without the necessary permissions cannot access PII data.
• You can create views that mask or exclude PII data for users who should not have access to it. This can be done using dynamic view functions, which return either encrypted or masked data based on the user's access level.

Modifying a table not owned by the user:

• Users cannot modify tables they do not own unless they have been explicitly granted the necessary permissions. Unity Catalog provides a unified permission model to manage access policies consistently across data and AI assets.

You can enforce access controls and permissions to prevent users from uploading files to the DBFS root. This can be managed through the Databricks workspace settings and Unity Catalog, ensuring that only authorized users have the necessary permissions to upload files to specific locations.

https://www.databricks.com/blog/2020/11/20/enforcing-column-level-encryption-and-avoiding-data-dupli...