Hi,
There is no existing code for this. Since gst-v4l2 is open source, you can add prints in output plane and capture to show the time the h264 stream is fed and the time frame data is decoded.
For profiling fps we can use fpsdisplaysink. For latency, would need to do manual steps.
Or may try like this:
Gstreamer TCPserversink 2-3 seconds latency - #5 by DaneLLL
If the network is stable, can check the latency in UDP streaming.