#1: From what I can tell, the screen order is based on visual layout in the canvas. It starts with the top row, and goes from left to right. Then it moves down to lower rows and again moves left to right.
#2: When you select the artboard in XD there are two heights to consider:
- The artboard height (H) lets you controls the size of the area you design on.
- Under Scrolling, the Viewport Height lets you define the height of the screen. When the artboard is taller than the viewport height, you should be able to scroll down to see the rest of the content on the artboard. If you don't see scrollbars in the preview, use the scroll wheel on your mouse (or scroll gesture on a trackpad, etc.).
Thanks for your help, Dan. Makes sense re: order of the artboards. For the scrolling problem, I found another response in the Adobe community where the person said to adjust the viewport height under the scrolling panel so that it matches the size of the artboard. I did this and when I preview the screens, some of the screens display in actual size along with the scroll bar to move down the page. However, for other pages, it reduced the size of the screen so that it fits into view. These pages are not readable now because all the text and images are too small. I don't know why the pages are not displaying consistently in actual size with the scroll bars.
You should not make the viewport height the same as the artboard. That's not how XD intended for those settings to work, and can lead to it scaling the artboard (as you experienced). Make the vieport an appropriate height for the width device the artboard is designed for (which should be shorter than a tell artboard). That way you can see what a user would see before they scroll. Then you should be able to scroll down to see the rest of the artboard.
Keep in mind that the preview is meant to show what users will experience. They won't see the entire artboard at a time, they may need to scroll. Hope that helps.