Seven days work best with two cities, or one city plus a nearby landscape. Starting in Beijing and finishing in Shanghai is possible, but only if each transfer day stays deliberately light.
Build around two anchors
Choose one historical city and one contemporary city, then decide what must be experienced in each. Avoid adding a third stop only because it appears on a classic map.
Keep arrival and departure gentle
Book the first evening close to your hotel and avoid a major attraction on the final morning. Those small buffers protect the rest of the week.