Summary of the outcome of the investigation:
If not already created, create a new solution. If a new publisher is created as part of this process, it is possible to change the prefix which is added to tables and other objects.
Set the 'preferred solution' setting in Power Apps so that a new site and its components are added to a solution and the solution will be updated as pages, roles... etc are added, updated, deleted

Set the 'current solution' setting in Power Pages so that any tables, views... are added to a solution and the solution will be updated as tables, views... are added, updated, deleted. This includes updates to the OOTB tables

I'll hold off accepting this as the solution for the moment, as I should be doing a bit more work which might throw up something else which is useful.