How robust is the security model?

How robust is the security model?

Everybody duck - newbie on board. I have a question about security and segregation.

I manage multiple accounts, with multiple projects, and with multiple employees/subscontractors. I'd like to be able to use a project management solution that allows me as the admin to track and see everything. But I also need to be able to completely segregate everything for everybody else. Account A cannot see anything about account B, people working on project A can see nothing about project B.

Can the security handle this? Can I segragate things well enough do that people that use my system will not have a clue about anything else I have going in my company?