Team members functionality
If you are creating a project then you definitely have a team. So, you can add team members to the project while creating a project, edit project or in overview sections. Team members get project requests sent by you through mail and can accept it and join the team.
Project History functionality
Small projects can be handled easily but if you have huge ones then? Project owner and manager have to maintain the history of that project, so Decision 168 automatically captured every move in that project and every one can see through the history section in the project overview. But as I told you, team members have some restrictions, that they are not allowed to filter and export history data but project owners and managers can.