iPad Pro

I use the Smart Keyboard Folio for iPad Pro For my iPad Pro. It is not cheap but I like it because it works well, It is the same size as the keyboard as my laptop so my fingers work seamlessly as I move from one to the other. It does not have to be charged and acts as a cover for my iPad to keep everything handy and safe.

“Best” is subjective.

Here is a link to keyboards compatible with the fourth-generation iPad Pro 12.9” that are directly marketed by Apple:

Keyboards - iPad Accessories - Apple

There are many other third-party keyboards that may, or may not, fit your needs or budget. Perhaps consider Zagg and Logitech - although there are many others.