Can my hero banner use a different photo on mobile than on desktop?

Yes. Images can be set per device.

1. Open the banner section in the builder. With the Desktop tab selected, set your wide image as usual.
2. Click the Mobile tab at the top of the panel.
3. In the same image field, click Browse and pick your tall photo.
4. Click Save.

On the Mobile tab, each field shows a small phone badge. It fills in once that field has its own mobile value, and a ↺ appears so you can reset it to the desktop value.

Images, backgrounds, layout, style and counts can all differ per device. The wording (headings, text and button labels) stays the same on every device.