The pyramidal framework of hierarchy:

Is typical of public organisations.

It is no longer common in practice.

Is the most complex to manage.

The horizontal framework of the hierarchy:

It is recommended for large organisations to reduce internal complexity.

It implies a peer-to-peer relation across all levels.

It is most common and recommended for small and agile organisations.

The format of the communication relates to:

The clarity of the message.

The way the content is introduced and presented to the interlocutor.

The relevance of the content.