A Microsoft file hosting and synchronization service.
Hi keegkeegkeeg:
You are welcome to post in our forum.
I read your post carefully, my understanding is you currently want to share the folder to another "team",and the "team"refere to other group (Learn about Microsoft 365 Groups ) , and you want some files in the folder to have custom permissions. Please let me know if my understanding is correct, if not, please feel free to correct me.
If my understanding is correct, I think you don't have to copy-paste your folder, but directly by sharing, members of another group can access some of the files in it. This will help you save time and manage your files more efficiently. Ref: Share OneDrive files and folders (microsoft.com)
If you don't want to be viewed by other users for the content in the subfolder, you can directly cancel the sharing of the subfolder through the access permission of the folder, so that other users cannot access these files. Stop sharing OneDrive or SharePoint files or folders, or change permissions (microsoft.com)
If you want other users to be able to access the file but not be able to change the file, you need to customize the file's permissions. I recommend that you upload the file to a SharePoint library and then customize the subfolder's permissions:How to list unique permissions for files and folders on a SharePoint site - SharePoint Maven.
Hope my instructions help you achieve your purpose. Please correct me if I understand something wrong, I will continue to investigate and do my best to help you solve the problem.
Best regards,
Tin