Why are KDE apps running on unity too slow to load
Solution 1:
You could say that yes, Evince and Gedit use GTK libraries, these are already loaded by the rest of the environment. Launching the KDE software means launching more libraries which take more time because they're not already being used by other software.
I wouldn't add anything to autostart as it will probably slow it down, once they're loaded when you open one your KDE programs you're good to go.