When exporting a video with Smart Rendering, does it matter what bitrate you use? In other words, if I was to export a video using a rather low bitrate but used smart render, then would the quality still be the same as the source?
Quite often if you are offered Smart Rendering, not all, if any of the video will be smart rendered. For that to occur the frame being copied and the exported frame must be denticle in every way. No fades and only straight cuts will also be smart rendered and not always seamlessly depending on the GOP structure at the points of the edit and throughout must be the same. There is a quite comprehensive explanation within the PDF manual. It takes some getting your head around it to make sense, if any.
So the short answer to your question is no. As it will not have been Smart Rendered regardless of the option being there if you alter the parameters of the export.