Do you want to replace your Web-to-Lead or Web-to-Case form with a Formstack form, yet do you still want to use Assignment Rules or Autoresponse Rules? No fear-- with Formstack's Salesforce App you can still have this functionality!
First, add your Lead or Case object to your form. Then, when searching for fields, if you type "Formstack" you will see the following fields appear.
Double click on these fields or drag and drop them onto your form. Both of these fields are checkboxes, and checking off the box will tell Formstack to trigger the rules.
The Auto-Assign checkbox will automatically assign your Leads/Cases, while the Autoresponse checkbox will send a Lead/Case Notification. By default, the field will be visible and the checkbox to trigger these rules will not be selected, so you will need to modify the field settings. You can access the field settings by hovering over the field and click the blue chevron to the right of the field.