How to make some of the form to come prefilled?

We are also looking for some of the form to come prefilled, and for some of the prefilled fields able to be overridden by the patient filling out the forms.

I understand that you want to pre-populate some of the fields on the form. The pre-population of the fields on a form is possible by following the guide Prepopulating-Fields-to-Your-JotForm-via-URL-Parameters.

You may also take a look at the prepopulate app that helps in pre-populating fields on a JotForm.

http://prepopulate.jotform.io/

Hope this information helps!