I just dropped the file into the editor tool and immediately published it using the YouTube option. I'm not sure what all that option entails, just says it will output it in 1080p
I think the problem you mentioned with quality is because you took the render direct to youtube option.. almost every editor I have used or seen lowers the quality when using this option. Try rendering it to a file first, view it, then upload.. if you find your uploaded one is alittle dark, just lighten or increase the brightness of the video and remember settings for next time. Also rendering to a file first allows you to adjust it to 1080p @ 30fps.
Personally I use Pinnacle Studio 16 Ultimate which is overkill for what I use it for, but it does have some cool stuff.
As far as shadowplay goes, best thing since sliced bread, however those guys with AMD cards, or pre 6 series might want to try msi afterburners version of it. Just download the msi afterburner beta 16. Go to the video section in settings and you will see a lot more options than shadowplay has.
I have done recordings using shadowplay at my normal game settings (lowest) and max graphics settings. There is a small drop in fps avg, but only 5-8 frames. You can run fraps at the same time to show your fps counter, and benchmark with fraps too while shadowplay is running. Just disable the video record feature, but leave the screen shot feature on so you can still use it.
I normally avg around 130fps on all maps, but with shadowplay turned on in shadow mode, it drops to around 125ish.. also I am using win8.1 and I think its affected the game alittle, especially with hit detection and input lag. Also I have asus 144Hz monitor too.