Elsevier's 'MethodsX' journal as an additional article to my original research article (plagiarism) I recently submitted a paper to an Elsevier Journal (Biomedical Signal Processing and Control), in the revision stage they propose to me to send a part of my work as MethodX article https://www.journals.elsevier.com/methodsx alongside my revised research article and if my paper accepted for publication the MethodX article will automatically be transferred to MethodX where will be reviewed and published as a separate article.

Now, If I prepared the MethodX article, should I change the original text, rewrite  (not be guilty of plagiarism) or just take parts from the original article and format a MethodX article?
The MethodsX journal says, as part of its guide to authors:


  Your submission can also be an extension of a previously published original research paper, whereas your MethodsX paper will include all of the technical details that might not have been included in your research paper.


It also has an extremely abbreviated format, 


  
  an abstract to outline the customization
  a graphical abstract visual to illustrate what you've done 
  the method(s) in sufficient detail to help people replicate it, including any relevant figures, tables etc
  at least one reference to the original description of the method you're using
  


Thus, for a properly prepared MethodsX article, I think that any question of plagiarism will be moot. Abstract and context material will need to be heavily paraphrased for its new context, and any repeated material on the method will be explicitly cited as an adaptation (with permission) of the original paper.