How do I restore the default offer letter

To restore the default letter template, go to Organization -> Edit Template -> Choose your Organization -> Offer Template

Then load the default template.

What is the difference between the Dropbox and Lob Template?

The Dropbox template places the organizational mailing address and the sellers address information in the correct spot. The Lob template removes this data as our mailing partner Lob will automatically apply the organization address and the sellers address in their top protected area.