There are numerous ways of slicing this answer but fundamentally you need to ask the question of yourself; is each of those platform elements a separate project or are they all linked to a common project which serves a common user or set of users and, crucially, how many developments teams do you have working on the things to be done?
My limited assessment is that you are discussing a single backlog of work which should be divided into Themes, Epics and User Stories.
You can find a more detailed explanation here: https://www.mountaingoatsoftware.com/blog/stories-epics-and-themes
User Stories
A user story is simply something a user wants.
User stories can and often are part of a larger collection of functionality which we refer to as Epics
Epics
A Scrum epic is a large user story. Similar to how a single movie can be an Action movie or a Romance movie
Themes
Finally, “theme” is a collection of user stories. We could put a rubber band around that group of stories I wrote about monthly reporting and we'd call that a “theme.” For instance all James Bond movies are part of a theme.
Projects or Teams
Once you have a healthy and well understood backlog, with some detailed stories and a simple categorization system for Themes and Epics you will be in a great position to understand how many development teams you need and how they should be structured.
The beauty of having a backlog is that teams can dip in and out of the themes and epics based on business value and priority rather than having to deliver entire functional areas.
You can find more information here but understanding the basics of Scrum will go a long way to helping you answer your own question which is the nature of the Agile values and the iterative frameworks within which we work.
Self Organisation
A key principle of the Scrum framework is that of self-organizing team which has autonomy into it's own working structure.
https://www.infoq.com/news/2015/02/establishing-self-organized-team
So ask the team how they think they should be structured.
