Should I use the Cloud Platform, or the Modernisation Platform?
You should refer to the MoJ Technical Guidance for how to host services.
By default, you must use the Cloud Platform unless you’re advised otherwise by a member of the Hosting team.
The Modernisation Platform is generally for applications that don’t fit into the Cloud Platform, which tend to be legacy applications.
For your specific use-case, you should contact the Hosting team who can help advise what you should use.