A neat trick I use to figure out what apps belong to what packages is to run realpath $(which $app_name) - this outputs the full, canonicalized path to the store item, which should include the package name.
I would do a search (e.g. using grep) through a local copy of the Guix repository to figure out what services are providing the packages, then modify the service configurations (or use modified versions of services, if needed) to remove them. This might be a tedious solution, though.