@scottxu actually there is one more thing for you to look at
It appears that even though your rtsp server uses the same encoding settings as used for whatever is set under "streaming output", it actually does its own separate encode. This increases usage of the encoder when doing running the rtsp server in addition to the streaming output or local file (when set to "same as stream")
It seems to me that both the rtsp server and the stream output should both be able to use the same encoded video. If this is not technically feasible, let me know.