I believe that if research pieces are varying from each other at least a bit (e.g. with methodology, results, applications) the papers should be submitted in different journals, even with narrower scopes.

I prefer to publish in different journals to expand the readership.

I think its is subjective. I do not mind publishing in the same journal, or different journals. However, I think it is best to find a journal that focuses on the research questions being addressed by the study in question.

I think, you are publish in different journals