Simple Start allows for 1 user and 2 accountant users.
Essentials allows for 3 users and 2 accountant users. (Includes Accounts Payable, time tracking users, multiple currencies, Basic user permissions, 1099 tracking, setup up invoices to automatically bill on a recurring schedule)
Essentials Plus allows for 5 users and 2 accountant users. (Also includes class tracking, budgeting, inventory, purchase orders, locations, multiple currencies, time tracking only users)
QuickBooks Online Advanced allows for 25 users and 3 accountant users (Custom user permissions, smart reporting powered by Fathom, Priority Circle membership, custom fields)