If you export your images without any resizing, you are exporting your images at full resolution. An image size is simply it's pixel dimensions. It doesn't matter what you set the resolution to. It can be 72, or 300, or 600. If you need an image that will print larger than it will be necessary for you to do the math and export an image with bigger dimensions. In other words, you will be resizing your image on export. For instance, let's say that you want an image that is 20 x 30" at 300 pixels per inch. 30 X 300 = 9000 pixels on the long side. 20 X 300 = 6000 pixels on the narrow side. It doesn't matter what resolution setting you put in the file. It won't make any difference. Usually larger images are viewed from a greater distance, so the resolution typically doesn't have to be as high. You could probably get away with 200 PPI, and no one would ever see the difference.