Short answer: Resubmission support is usually scoped from the editor or reviewer comments, the revised manuscript, and the amount of rewriting or language work needed. A few minor comments and a major revision are not equivalent jobs.
Send the decision letter, all reviewer comments, the latest manuscript, and any response draft you have. This allows the provider to identify whether the work is language editing, response-letter editing, formatting, or a broader revision-support task.
The author remains responsible for the scientific response to reviewers. An editor can improve clarity, tone, organization, and consistency but should not invent data or responses.
Confirm whether the service includes a cross-check between the response letter and revised manuscript so that stated changes are easy to locate.