You can always share files and other resources as your own user. This is intuitive, convenient and gives you direct control over who has access to those files. However there are times when it makes sense to create a special user for sharing Nextcoud resources instead.
People can cycle out of specific roles at an organization or move on. If that person's Nextcloud account is closed and deleted everyone within your organization or project who they shared files and resources with will lose access to those shared files. Unless a lot of care and planning is done to transfer ownership of those files to a new user before they leave the organization the sudden loss of shared resources can be disruptive.
To avoid the above situation we recommend creating a special user just for sharing resources. In reality there's nothing "special" about the role user only that this user won't correspond to any real person within your org, it will be created as a hub for files and resources of the organization as a whole or for a specific project. You can just create a new Nextcloud account like any other. Give this user a special name to indicate its use like yourorg-share or yourproject-share.
Login as the special user to create Nextcloud teams, share folders or calendars. From this account share the resources you want with any teams or specific users that should have access. Creating a shared folder is convenient because other users with access can just add files they want to share with everyone else to that folder.
Using this method, you or anyone else can leave the organization or move on from a project and as long as the special share user persists, there can be an easy and smooth transition to maintaining shared resources.