Disable CkEditor to body field of a content type
The problem you experienced with configuring the field is that in core there is no option to select the allowed text formats. When this module is installed

https://www.drupal.org/project/allowed_formats

you can select the text format that is available for a specific field and then you can choose in the settings of the text format whether to use ckeditor or not.

There is work going on to put this in core: https://www.drupal.org/node/784672