Hmm I've never heard of an ElGato. The results it produces are quite good though. I personally use a Hauppauge HD PVR and Sony Vegas 12 to render my videos.
My first suggestion would be don't render your videos in 1080p resolution unless the actual recording is. So in this example NUNSG is 720p resolution so render with that just to reduce file size of course and save time.
When rendering use either MP4 or WMV format, they produce the best results. Sony Vegas is the BEST by far I think. The editing capabilities are great.
I noticed you removed NUNSG sound completely, in the options of that game you can remove music and keep SFX which is great for videos with custom BGM. Check out my online battles for NUNS3 and look at the editing in regards to sound.
I also noticed your comment about HD PVR's

tell me what you think of the quality of my videos because HD PVR's are all good but the rendering of videos is what makes them finished professional products