Great to hear you want to add USPS shipping to your store. I think that you should call it expedited shipping and list the average number of shipping days. This is because you don't want your customers to be misled about what it means. For example, I think of expedited shipping to be between 2-3 days personally.
Finally, I would definitely not add insured to either of those unless you have insurance set in place for your business. If you don't have insurance, you can cause many more problems for yourself by falsely claiming it is insured! Just want to be transparent so you don't run into any legal trouble. Hope that helps!