I use USPS shipping. Buyers choose whether to have item sent First, Priority or Overnight unless the weight of the items makes one of the options unavailable. For instance, prayer shawls cannot be sent First Class because they are over the weight limit.
International customers are responsible for all fees, tariffs, taxes, etc. to their own country. Custom fees may be assessed by a country and those costs are the responsibility of the buyer.
Because each country has their own procedures, delivery dates may be impacted. International orders will contain a customs number. The buyer can use it with their customs office to try and track a package. Full value is declared on every package - every time - even for the royal family.