NVENC vs Maincocept openCL H.264 encoder

Hi there,
In our project we are capturing directx windows (games) and feeding them online to a H.264 encoder and then transmit it over the network. the encoder we are using now is mainconcept opencl h.264 encoder. then multiplexing it into a transport stream using mainconcept muxer. but we are not satisfied with the peformance and wondering just if NVENC can have a better performance. can somebody please help?? and also what is the output of NVENC? I mean it will generate bare H.264 frames ot it has options to encapsulate frames in PES and TS packets? any help, hint or idea will be much appreciated. thanks in advance.