ZombieBrain
Always hungry!
Usually you'll want to record at 15-20mbps then export at around 8-9. Exporting at 15mbps won't help much though, it'll just create a bigger file, which is why it's better to pick a data rate to export at closer to the compressed rate. I have noticed though; that if you record at 8mbps for a 1080P vid, then export and upload at 8mbps it does look worse.
That's interesting. I have to do some testing myself. I have my Shadowplay set at 60mbps (the file sizes are still pretty small so it doesn't bother me) and then I encode my vids at 15mbps. The final file size isn't tragic though (around 100MB per minute).