Yes. One can have only one EAD at a time as they track your EAD based on the Alien number. Check A- number in both of your EAD (TPS and OPT), it should be same.
One of the benefits of using OPT Card is tax exemption. Certain tax you do not need to pay. suggest you to research based on this and notify your employer to amend in your payroll. You save some money.