(co-founder of Neptyne here)

With Google Sheets you get a flavor of JS called Apps Script, a flavor of JS with some limitations. Some ways in which our use of Python differ are:

- run Python directly in the spreadsheet cells, not just as an "extension"

- a full runtime in a Jupyter kernel, so you can import and use effectively any Python package, as long as it runs on Linux

- an interactive REPL that gives you a nice test environment, but also a command line of sorts for working with your spreadsheet. (e.g. you can say `A1 = requests.get(URL).json()`) to do a one-off fetch of some data from an API.

Generally speaking we hope to give you a much more powerful/seamless integration between spreadsheet/Python than what you get with Sheets/JS