There's definitely some overlap!

Gridstack is a great tool for building complex grid layouts with drag and drop for specific use-cases.

Puck is for creating a complete page building experience, which includes not only drag and drop, but also user input via fields, viewport previewing, APIs for fetching data, etc.

Gridstack also provides it's own grid system, whereas Puck currently is unopinionated, supporting any component library that uses `display: grid` internally.