nvcamerasrc is deprecated from L4T 31.1 which though supports only Xavier.
But following 32.2, also supporting TX2, has only nvarguscamerasrc.
So your development is better based on nvarguscamerasrc.
please refer to Sensor Driver Programming Guide for the [Control Handlers] session,
the unit of the exposure-time controls is seconds.
there are exposure-time boundaries definition, you should also check sensor device tree properties settings.
for example,
/kernel_src/hardware/nvidia/platform/t18x/common/kernel-dts/t18x-common-modules/tegra186-camera-li-mipi-adpt-a00.dtsi
normally, sensor sensitivity (ISO) is controlled by sensor gains. there are two types of sensor gain, analog-gain and digital-gain.
since digital-gain always introduce lots of noise, we usually waive it for better image quality.
you could also refer to imx185_set_gain() function in the sensor driver to have more details.
/kernel_src/kernel/kernel-4.4/drivers/media/i2c/imx185.c
AE region will affect sensitivity, since CameraCore library calculate the suitable AE settings and these new settings will also apply to corresponding frames.