Auto-rickshaws and app taxis are the practical way to move between sights. Distances are longer than they look on a map, traffic can be slow, and the river, railway lines, and old industrial zones break the city into awkward pieces.
The metro is useful for some central corridors but does not yet solve every tourist journey. For Phool Bagh, Nana Rao Park, Kanpur Central, and the Mall Road area, walking short stretches is possible once you are there.