Kaifeng Museum is the best single stop for putting the city in order. Kaifeng's fame rests on its Northern Song capital years, but the museum also helps connect that grand period with Yellow River disasters, later rebuilding, and the city's unusual Jewish history.
Go before the theme-park-style historic areas if you can. The museum gives you the names, maps, and objects that make Kaifeng feel like a real former capital rather than a collection of reconstructed gates and snack streets.