CQRS is not a pattern that encompasses the whole application.
It is a concept that builds on Domain Driven Design (DDD). And an important strategic concept of DDD is the so-called Bounded Context.
In a typical application there are multiple bounded contexts, any of which can be implemented the way it makes sense. For instance
- User Management -> CRUD
- Invoicing -> CRUD
- Insurance Policy Management (the Core Domain) -> CQRS
- …
This probably doesn’t answer your question but it might give a little more insight into the topic. To be honest, I don’t think it can be answered at all without considering a project’s specifics, and even then there is rarely something like a definite best practice.