I don't have that info at hand, but I suggest before doing 64TB you pick a smaller set of files and use those for testing. At various resolutions, evaluate visual quality, transcode time, encoded bit rate, file size, etc. Verify relilnk works at the final encoding chosen, esp. if on a different volume name and using different file paths.
Don't do 64TB only to find there is some issue with audio, file path or encoding format that prevents relink.
Never found a way to determine data rates in FCP unless I export a file and peek inside. That 15 mbps is about right. I use Compressor to reencode files. That way I can get the max data rate (19,531) for a 264 file where punting the same from FC only gets you 15,000. Compressor allows you to dial in whatever rate you please.