Forcing transparency and blur

#Window decorations only

To get translucent titlebars, you need window decorations that are translucent, and the blur effect turned on in the Desktop Effects module. The Window Decorations module has a Titlebar opacity setting.

#Window body transparency

#Keeping your current style

You don't need anything extra to make windows translucent.

Create a window rule: press Alt+F3, then choose More Actions > Configure Special Window Settings…. Set Window class to Unimportant. Also select all window types apart from Desktop and Splash Screen, so that the rule applies to everything. Add the Active opacity and Inactive opacity properties and Force them to the amount you want.

Create another rule above the first as an exclusion. Separate the window classes with |, for example conky|pqiv|sonicshell, set Window class to Regular expression, and force the opacity to 100%. If you don't know a window's class, use Detect Window Properties. See Detect Window Properties.

#Kvantum

Kvantum isn't part of SonicDE, but you can install it from its GitHub page. Choose the Kvantum style in the Application Style module, then choose a Kvantum theme in its separate application, Kvantum Manager. To get blur, install a Kvantum theme with transparency, and choose it as your current theme.

#Blur

The blur effect blurs behind windows that ask for it. A script that runs at startup can ask for it on behalf of an application's windows, by setting the _KDE_NET_WM_BLUR_BEHIND_REGION property. This needs the xdotool and xprop tools:

if [[ $(ps --no-header -p $PPID -o comm) =~ '^yakuake|sonic-ecco$' ]]; then
    for wid in $(xdotool search --pid $PPID); do
       xprop -f _KDE_NET_WM_BLUR_BEHIND_REGION 32c -set _KDE_NET_WM_BLUR_BEHIND_REGION 0 -id $wid;
    done
fi

SonicWin scripts from the KDE Store can do the same thing. Manage them in the SonicWin Scripts module.

Menus are the exception: Blur menus in the blur effect's settings decides for every see-through menu, whether the menu asks for blur itself (as Silver's do) or is made see-through by the Translucency effect. Turned off, no menu is blurred.