Are all expenses created equal? As in, should I create suppliers for all my purchases and payments and record here? i.e…rents, supplies, city taxes, phone, manager fees 
etc. except for payroll and subcontractor pay which goes under pay slips. Thanks!
Under Suppliers tab, you should only add suppliers where you purchase on credit.
All suppliers who send you bills that are to be paid at later date should be created under Suppliers tab. When they send you bill, the bill should be created under Purchase Invoices tab.
Reminding suppliers where you pay at the time of purchase (e.g. stationary shop) don’t have to be created as Suppliers. When you pay them, simply go to Bank accounts, Cash accounts or Expense claims and record the expense there.
Also, subcontractors are not employees. Subcontractors will send you an invoice which is to be paid by due date. So all subcontractors should be created under Suppliers tab too. And their invoices under Purchase Invoices tab.