Can a team member or team leader user add new companies, people and deals?

Yes, All users (except read-only or external users) on the account can add new People, Company, and Deals. People and Deal owners default to the user adding the record; Company records must be assigned by Executive users. 

If the Company owner is a required field then the user adding the record will default as the owner. If a non-Executive user adds a new Company and the owner field is not required, the owner field will default to 'none.'