Don't work look-and-feel

[WeedMan]

Hello. I wrote three simple application where the system displays the FileDialog. The results are different and none is purely native.
Use QApplication and QQuickView or QFileDialog(without QML):

Use QGuiApplication and QQmlApplicationEngine:

FileDialog(native) open through KWrite:

How set look-and-feel/localization like as in current system?
Why are the results still different when using QQmlApplicationEngine and QQuickView (qml-file used by the same)?

I use PySide2 from pip
Qt 5.11.2 from system
Clang 7.0.1 from system
DE: KDE5

[WeedMan]

I tried set style Fusion but style app not yet perfected

[WeedMan]

I have Qt/PyQt 5.11 installed from repositories. I run QFileDiaolg from pure Qt app and PyQt5 and now looks as it should
I guess if Qt build for your system then should not be problem, else may be roughness with looks and fills (post above)

Qt app from example:

PyQt5 app:

Maybe there is still some way to give the program the current system style or is it set only at compile time Qt for OS?