Understanding the module

Problem/Motivation

I have few questions:

1. So I can manage everything from drupal?

2. After installing this module, any user can chat any user or I can have certain restrictions? I have used rocket chat sometime ago and every user was able to chat with any user. Everything was open.

3. In my use case, I have a service provider portal. There are different service providers. The system will be based on appointment booking. And when they have a client, I want them to be able to chat and call with each other. Otherwise no.