There isn't really one way to do OKRs - you can read a dozen different descriptions and have a dozen variations. It's not a formal methodology but rather an approach that for a long time was passed around organically based on some key adjustments to MBO (Manage By Objectives) which came before it.

E.g. How Measure What Matters and Radical Focus describe OKRs - two of the most popular books on the subject - differ quite a lot.

I think finally there's some consensus that cascading OKRs is a bad practice but unfortunately people keep.doing it because that's how it was described in MWM.

We tended to have goals / OKRs per team and longer term goals they could align to. Flatter the better when possible.