I just worry that people often concider "best practices" as "the only docs that I have to read".
I mean there are many parts of Kotlin coroutines and Kotlinx coroutines especially that hard to put to a short "best practices", maybe "Common pitfalls" would be good too, like infamous "why blocking CommonPool is bad", but all those things are actually will change soon (with shared pool dispatcher)
Also maybe make sense to invest to shorter version of guide for beginners, but honestly not sure why Coroutine Guide by example is not enough for this.
But maybe would be nice to separate channels to a separate doc (separate lib?) and also improve channels docs with examples of common patterns
One more useful thing would be a document that uses RxJava as example for explaining coroutines what is different, how to replace some operators and so on, just because it's most popular lib for async programming at least on Android