Sharing a file to Workplace using a cloud storage integration doesn't affect the permissions of that file. If a member of your Workplace community doesn't have permission to view a file, they won't see a preview or have access to that content.
How do I see which Workplace integrations have access to my information?
How do I check which permissions the Workplace integrations I've enabled have access to?
Who has permissions to see a preview of a file shared from a cloud storage service on Workplace?
What happens if I change the permissions on a file stored in a cloud storage service?