Setting bitrate is normally for outputting the final result. Higher is always better except that all devices don’t accept all bitrates. 15Mbps output with the h264 codec is a safe choice for UHD and is the default for iPad and iPhone video.
If your display device will handle it, 45 Mbps is a good choice. BluRays are often encoded at that rate.
Streaming from VIMEO or YouTube will re-compress your footage to their standards anyway.