Drivers are present either as built-in into the kernel or as modules in the hostOS, whereas gstreamer with libraries and plugins, nodejs and other application components reside in the container, as you see in the Dockerfile example.
Now, I’ve looked into the documentation provided by the company that produces this camera and it looks like they provide a customized pre-built ubuntu image to be flashed on the TX2 that contains a customized device tree, specific binaries & libraries as well as a patched kernel with a different defconfig to have the camera running. This software bundle is provided along with the camera on an sd-card.
Since kernel changes are necessary to have this type of camera running with balenaOS, you can build your own image from sources in which you patch the kernel with the patches provided by the camera vendor in the camera software release bundle. You then flash the TX2 with this resulting image and unpack the camera vendor provided BSP archive inside the container, just like in the Dockerfile example I provided for you.