Not sure how to approach debugging this problem - assistance would be appreciated!

I have just installed Fedora 20 on an SSD with non-LVM partitioning, and both gnome and kde are not quite right, but my preferred manager, kde, is pretty much unusable. The failures take place for both my own 'user' as well as for 'root', which I used to try to determine whether the kde settings for 'user' could be corrupted. Sometimes the display wigs out on the login, but if it does work, it flickers quite a bit, and trying to watch an mp4 sends it into the toilet for sure.
The system I am using has a non-standard NVIDIA chipset on the motherboard, so I have always used NOUVEAU in the past, for other linux installs.

xrandr shows:
Screen 0: minimum 320 x 200, current 1920 x 1200, maximum 4096 x 4096
VGA-1 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 519mm x 324mm
1920x1200 60.0*+
1600x1200 60.0
1680x1050 60.0
1280x1024 75.0 60.0
1152x864 75.0
1024x768 75.1 60.0
800x600 75.0 60.3
640x480 75.0 60.0
720x400 70.1


In the xorg.0.log, I see numerous failures, but ultimately get sets of modelines that look like they should work?
[ 386.457]
X.Org X Server 1.14.4
Release Date: 2013-10-31
[ 386.457] X Protocol Version 11, Revision 0
[ 386.457] Build Operating System: 3.12.8-300.fc20.x86_64
[ 386.457] Current Operating System: Linux valhalla 3.13.8-200.fc20.x86_64 #1 SMP Tue Apr 1 03:35:46 UTC 2014 x86_64
[ 386.457] Kernel command line: BOOT_IMAGE=/vmlinuz-3.13.8-200.fc20.x86_64 root=UUID=d8d1465a-d8d8-4e8d-86c0-83d2e4bcf888 ro vconsol
e.font=latarcyrheb-sun16 rhgb quiet LANG=en_US.UTF-8
[ 386.457] Build Date: 28 February 2014 03:35:50AM
[ 386.457] Build ID: xorg-x11-server 1.14.4-7.fc20
[ 386.457] Current version of pixman: 0.30.0
...

Can anyone point me to what I should look at to make some headway here?
Thanks!

Does disabling compositing help? The Nouveau driver isn't known for being the best for compositing.
Also, is the system visually stable at something very basic - such as a TTY?

Thanks. I was unaware of Composite, but have disabled it, and verified this through Xorg.0.log, but the screen flicker is actually worse, and my first attempt to start the system into kde resulted in a frozen system. ??

Are you able to boot the system and have it stable at a virtual terminal (ie. no X running)?
If that works fine, does starting a basic X session with just a basic terminal (xterm) yield a stable system still?

please attach a full Xorg.0.log

We can close out this thread. Thanks for your help. In desperation I did a complete re-install with reformatting, and then immediately went to the nvidia site and worked google to determine whether there nvidia drivers that could work. There were (304.xx legacy) !

Thanks again!

I've now marked this topic as solved.