You can! First, we'll go through how to add alternative dimensions. In the right-side panel, add the dimension you'd like to be the alternative, in this case we'll use Region.
Once that has been added, in viewing mode, you'll see an arrow dropdown by the dimension label in the chart. When you switch between the dimensions, the narrative will update to use the dimension selected.
Adding an alternative measure is a little trickier and a bit more manual. To do this you start by adding the alternative measure the same way we did dimensions, in the right-side panel.
Now when you flip to viewing mode, instead of using the dropdown menu by the measure label, you need to open the "Exploration Menu" to select which measure you'd like the narrative to use. You can find the Exploration Menu by right-clicking on your chart.
In the menu, you'll see your measure options. Select the one you'd like the narrative to use and click Apply at the bottom.
You should now see a narrative writing your alternative measure.