Deanna you sell fabric right? Pat also sells some fabric. I'm sure she could help you if you have questions.
Just remember when you set up a profile, you can add First Class, Priority, Parcel Select - Express services. Whatever you like or usually ship with. The calculator is going to add the weights together so if it goes beyond FC parameters, it will jump to Parcel Select and Priority - but only if you also have those options selected.
It will show the customer the cheapest option first. In the cart there will be a drop down menu for the other services if they want to choose that.
Here is how to set it up
https://www.etsy.com/help/article/6131This is about Package Preferences
https://www.etsy.com/help/article/6167