Hi Srini,
As I mentioned, TM is only a NW addon so if you are already deployed EWM on SCM server then you can't install TM on the same instance. EWM can be deployed as SCM addon, ERP Addon and NW Addon. If you have deployed EWM as NW addon then you can install TM also on the same instance.
if you go for TM as standalone which you have to in your current EWM deployment, then you need to connect the TM and EWM using PI or web services. But in terms of functionality, TM will provide you same functionalities in both the cases. I hope it clarifies your question.