hello jfk214,
Q1
it should be, you may have quick try to compare the CPU usage by disable the camera preview frames rendering.
for example, $ gst-launch-1.0 nvarguscamerasrc sensor-id=0 ! 'video/x-raw(memory:NVMM),width=1920, height=1080, framerate=30/1, format=NV12' ! nvvidconv ! 'video/x-raw(memory:NVMM),format=I420' ! fpsdisplaysink text-overlay=0 video-sink=fakesink sync=0 -v
Q2
yes, 3A means auto-focus, auto-exposure, auto-white balance… such camera controls. you may try enable camera stream with argus_camera application, there’s user-interface for you toggle the AE lock, please try enable AE lock and you shall see slightly CPU usage drop.
Q3
sorry, we don’t public the sources code of /usr/sbin/nvargus-daemon.
you may download MMAPI via APT server, $ sudo apt install nvidia-l4t-jetson-multimedia-api to get the sources of argus_camera application.