We usually work and deliver projects in waves. If we do, then the first wave is the core box plus some add-ons or a miniature expansion. Unless we specify otherwise, Stretch Goals come in the second wave. It may vary though, so please always refer to the Updates section of a given project. For instance, ISS Vanguard had Stretch Goals spread across a couple of boxes. But then again, in The Kings of Ruin, all the Stretch Goals were already included in the core box.
Some smaller projects don't come in separate waves, but even then it's important to keep in mind that we are working on different language versions separately: English always comes first, and 6-8 months later, we are shipping other language versions that we call the LANG (other than English) wave.
As for the shipping methods, there are also two, provided we are having a two-wave project. If that's the case and you pick a single shipment method for your pledge, your whole order will be shipped in the second wave once everything is ready. If you get a split shipment, you will receive the core box and some add-ons in the first wave. The same applies to LANG versions.
It's always best to follow the Updates for the latest info about the development and shipping status.