I would like to create a new set of users in the organisation to be able to access reports / data pages but not be able to create new projects or edit existing ones. Is there a predefined user type for this purpose, or is there a way to create this type of user?

I think disabling survey platform will help, but you can check for one user and go forward:-

We have one called “Participants” which are for dashboard users. or you can create your own and add people to that role.