Sharepoint Online Templates / Provisioning.

I’d be happy to share my experience. We developed custom SharePoint Online provisioning framework approximately four years ago, based on our organizational use cases. It’s a fully script-driven model that enables consistent, scalable site creation and configuration. Key components include:

• CSV-Driven Configuration: Each provisioning activity is driven by structured CSV files, which define the configuration, schema and inputs. Custom PS Scripts read these files to dynamically build or configure the site components.
• Site Creation: Sites are provisioned using SharePoint OOTB templates and are associated with Microsoft 365 groups. All provisioned sites are associated with a designated Hub Site, to inherit the theme, color, navigation.
• Metadata Architecture:
  • The Global Term Store is leveraged for taxonomy for enterprise-wide metadata reuse
  • Global site columns and content types are defined centrally in the Content Type Hub for tenant-wide reuse.
  • Local site columns and content types are created based on specific business needs.
  • List and library-level columns are added dynamically to support unique metadata requirements.
• List and Library Provisioning: Lists and libraries are created with attached global content types and local site columns, list/library level columns
• Permission Model:
  • Custom permission levels are defined and scripted.
  • Library-level permissions are assigned (if applicable)

This model has enabled us to streamline site deployment and support repeatable, scalable provisioning across our tenant.

Please refer to below URLs for your use case:
https://www.enjoysharepoint.com/export-and-import-sharepoint-online-site-as-template-using-powershell/
https://laurakokkarinen.com/auto-configuring-sharepoint-sites-with-site-templates-the-setup-from-start-to-finish/