Can design my signup form beyond the tools that I'm given?
Yes, you can add both a welcome and thank you message to your survey, as well as customize the content for these messages.
On the top right corner of the Survey element, you will see a menu button. Clicking that button will open a dropdown menu that has options for creating these emails.
Any package that includes both survey and email should be able to make use of this feature.
These messages are a part of the nurturing process, and are important to making the customer feel valued and aware that you are using their data. Small gestures like this contribute to an overall feeling of being valued and respected. This makes customers want to stay with you and your business.