Confused about sync between Zoho Project and Zoho People

Confused about sync between Zoho Project and Zoho People

Hi, I am confused about the timesheet sync between Zoho Project and Zoho People:

  1. Is the sync bi-directional?
  2. How often does the sync happen?
  3. Is there ever a reason the time in Zoho People would not match the time in Zoho 
  4. Do users have to submit the timesheets in Zoho People?
  5. I have the integrations enabled in Zoho Expense for both People and Project.  But if I include the projects in Zoho People, then they seem to appear twice in Zoho Expense... 
  6. I am unclear but I would want to ensure that doesn't also happen in Zoho Books
What is the best practice for how this integration should work and where employees should log time?

Please clarify and advise.