For the warnings, they are normal, as a live stream has no duration and position cannot be computed.
For latency, lowering the value may not give the best result. Try to increase to 500 ms, it may finally be better.
Displaying to a window takes time. This depends on how you display and the libraries used for that.
cv::imshow is not very fast on Jetson, so for high resolution/framerates it may slow down the loop.
It may also depend on the graphics backend, if opencv highgui is using GTK or QT for example.
An alternative is to use a cv::VideoWriter with a gstreamer pipeline to a gstreamer display sink. Check this post.