Re: how to totally get rid of nvidia-settings configurations on login
The 302.* drivers introduced RandR 1.2. Some desktop environments, most notably GNOME but possibly also KDE (I haven't checked), have code in them to automatically reconfigure your displays using RandR 1.2. This code doesn't run on 295.* and older because those drivers don't support the new interfaces, which could explain why installing different versions of the driver results in different behavior.
After logging in, could you please run "xrandr --query" and paste the output here?