Is there a way to set a different default font for fields?
You want the fields in DocuSign to match those in the underlying document. When you add fields to your documents, you can set a variety of properties, including setting the font, size, or color for a text field. However, you don't want to have to define the properties each time a new envelope or template is created.
Create your own Custom Field that has all the font formatting defined. These Custom Fields can be used in sending and when creating Templates.