DahMainahGaimah :
My problem with Shadowplay is that it has audio issues and saves files in the mp4 format, which is absolute hell to edit. (Seriously, there is no good free editing software for mp4, and I REALLY don't want to learn AVISynth.)
1) MP4 is only the container, the video is H.264 which is standard for many devices.
2) OBS also uses the NVidia encoder and can output to both MP4 and FLV containers.
3) The container can be converted using other software to whatever you need likely. I know you can use MKVtoolnix for example to go to MKV at no loss to the video or audio content (it just swaps containers).
4) FRAPS video format?
I looked it up at fraps and couldn't find out. Wikipedia just says it's a "proprietary format" though I guess if you can edit it the software knows what it is somehow.
I think FRAPS recommends converting to WMV.
5) MP4:
There are LOTS of editors for this so I'm not quite sure what the issue is. It's one of the most common formats (i.e. AAC + H.264 in MP4 container)
6) Free video editors:
(many but not all of these support MP4)
http://www.ezvid.com/21-best-video-editing-software-for-free-download
I use NERO which obviously isn't free but it does work quite well. You can get the entire suite of software on sale for $65. Nero 2015 Platinum:
http://www.nero.com/enu/promotions/sea_2015/nero-2015-platinum-upgrade.php?NeroSID=3df7e5081a4348e437621d248d1e934a&cbtr=g-ca&ecid=ppc.am.can.n2015.go.can-enu-kw.cnd_en_brand-alone-exact.SEAG.R12689
7) *FRAPS STUTTERING*
One possible cause is that you need an SSD for the write file instead of an HDD. You can try dropping the quality to the LOWEST supported on your HDD to see if stuttering drops. If it does it's probably a write speed issue.