Drag and drop files into document libraries to migrate documents. SharePoint Online Document Migration Options.
SharePoint Online upload options. Default Upload
A Document Set is a group of related documents that you can manage as a single entity. You can create a Document Set in a single step, and then define its characteristics and metadata. You can manage the set as a single entity.
Custom permissions in SharePoint Online.
If you are working on a hub site that publishes content types to other site collections, you can publish, republish, or unpublish content types centrally across all site collections.
Content types enable organizations to organize, manage, and handle content in a consistent way across a site collection. By defining content types for specific kinds of documents or information products, an organization can ensure that each of these groups of content is managed in a consistent way. Example: If you have a company template (company logo, address, phone number, email address etc.) that should be used on all the documents. Not all your employees might add the desired properties in the same way.
SharePoint Online columns
Document collaboration means several authors work on a document or collection of documents together. They could be simultaneously co-authoring a document or reviewing a specification as part of a structured workflow.
Checking out files before working on them helps to avoid conflicts and confusion when multiple people are working on the same set of files.
Assigning permissions in SharePoint