Would the Jetson Nano VPU be fit for our project

Hi,
It does not add filler data. Since gst-v4l2 package is open source, you can download the source code and add it. Please download the package:
https://developer.nvidia.com/embedded/L4T/r32_Release_v4.3/Sources/T210/public_sources.tbz2

We have seen limitation that it cannot go lower than 1.5Mbps for 1080p30:

So for certain cases, it may not be able to go down to 200kbps.