The picture helps a little, but I’m still confused by what you’re saying.
It looks to me now that you shouldn’t be working with Model forms at all. Since you’re pulling (feeding?) data from (to) different Models, you may just want to use a form and do the association between the forms and their related models in your view.
Make sure you’re clear in your mind the difference between your models and your forms. Models are the representation of your data in your database. Forms are the representation of your data on a web page. When your web page closely aligns to your database, then ModelForms are appropriate. Otherwise, you want to manage those relationships yourself.
So I think when you are making references to ModelForms, you’re actually just talking about your models, correct?
Am I getting close?
Also for clarification:
Is wrong. Formsets are for replicating the same form, not necessarily the same model form.