Does anyone have a preference between the various static typecheckers for Python? I.e. pytype, pyright, mypy, pyre?

Ideally something that handles Numpy sensibly, is well documented, and doesn't require inline annotations (i.e. can use .pyi files)

Pylance supports .pyi files.

As a side note, I've been wishing for a plug-in that would keep the annotations separate from the code, in .pyi files, but transparently integrate them into the editor. I.e. I would write the annotations as part of the code, but on a save they would be removed from the .py file (while still being displayed in the editor) and save them to .pyi.

I would write such a plug-in for PyCharm/IntelliJ myself if I had more time on my hands. :/

and pylance uses pyright to do so.