NvEnc with variable bandwidth?

Usecase: Streaming for 4k

  1. I am using nvenc (CBR mode H264) for streaming use case. While the network bandwidth fluctuates, what is the best way to reconfigure nvenc? Do we adjust the QP settings to higher value (i.e. lower down the quality) or adjusting the BW to lower value is sufficient?
  2. Does the nvenc bandwidth need to be configured separately for different resolution to avoid congestion? Are there any guidelines on that?