There are no limits to the amount of Admins or Superadmins an account can have.
Configurable roles (Standard, Admin, or Superadmin) are available for all plans.
To edit user roles, go to Configure > Users tab > 3-dot menu > Edit user > Role > Save:
Need a hand? Contact our friendly Support team via the in-app chat at the bottom-right of your screen, or email firstname.lastname@example.org.