I expect the source version will be the same as the gitlab-ce version. I can only find such options for enabling/disabling features under the project itself Settings --> General --> Visibility, project features, Permissions. Here you can disable wiki, CI/CD, packages.
There isn’t anything under global server settings as far as I can see. For me this isn’t an issue, since I’m the admin of my server, so when I create new projects, I disable the functionality. Of course, a person with enough privileges in that project could potentially re-enable it again.
It would be nice to have it at a global level, maybe it will appear sometime soon.