The employer registration type is the default user account, with the option to allow Job Seeker registration. Although you can disable registration from the main
wp-admin, this in turn would also disallow Job Seeker registration. There is ultimately no default option which would prevent Employers registering as well as Job Seekers, so it would require customization of the default theme on your part if you were looking to change this functionality.
By default, you can charge users for listing jobs, or viewing resumes, but again it would require customization if you wanted to make changes to existing pricing options as you describe. It can technically be done, as there is no encryption which would prevent you from making such changes, but there are no options built into the theme for these. Thanks.