You may want to restrict the ability for your submitting users to edit form or case data. You can manage this within the workflow by setting case values. Below are the values you should set on the case. If set to true the user will be restricted. If set to false the user will be able to modify data (default).
From within the Case view, users will be able to open and view the form but not modify form field values or save the form.
From within the Case Edit popup, users will not be able to click the case delete button.
From within the Case Edit popup, users will not be able to modify the case create form field values or save the form.
If you want the ability to manipulate the form field values while restricting the user, create a worklist. In your new worklist add the forms you want to manipulate. You can then add a case to the worklist and manage the data in the forms.