hi @Marsturix when you run from studio the render request executes always on preview mode so the results of the render give you the preview mode of the docx. when you render from the http api you should get the normal docx and not the iframe preview version
I think if you want to force to not use the preview mode when you run from the studio then you can pass in the options
let options = { "preview": false, "reports": { "save": true }, }