You can use whatever inherits you like for the folders. Just open the index theme and change it. Wallpaper in screenshot is the KDE on Leather wallpaper found here:
https://www.opendesktop.org/p/1296138

My folders are using the newaita-dark icons for the inherits and they are here: https://github.com/cbrnix/Newaita

The original folder icons are the Laferte icons here:
https://www.opendesktop.org/p/1301692

More screenshots are here:
https://github.com/freefreeno/Matrix-Plasma-Color-Scheme-and-Plasma-Theme-Along-with-Folders