Isn't there already a Brazilian national team of some sort with that same name?
No, ARC-77. These were just personal identifications - not a clan tag. In example, the player Furacao belongs already to the team, but with no need to change the name. And about giovanni.br, we had any contact about this.
The list of the members can be found here:
I think the wikia is the most secure way to know about real clan members, with all these impostors outside. Anyways, if giovanni.br see this, feel free to join the team. We played a few games together and he is a good player.