Properly changing window styles under awesomewm

[ghost]

I have been using awesomwm for the past 6 years, I wouldn't think about moving to any other environment. I am using it on this machine under ubuntu. Here is my issue:

If I open a pdf in Okular, the scroll bar is very difficult to see:

If I switch awesomewm with KDE Plasma, they are much more clearer to see:

When I open the KDE settings app in awesomewm, no matter what I change, it won't be applied, the default window styles and scrollbars will never change:

How can I properly change window styles and scrollbars to ones with higher contrast (changing to KDE ones is good). Thanks.

[ghost]

I have simplified my question here:
#3915