After installing the theme change color scheme to "ArchBandW" for better experience.
Suggestions to improve this theme are always welcomed
Select "Use desktop layout from theme" before applying theme.
Kvantum Themes available with same name.
The Theme supports three modes : Translucent, Opaque, Adaptive
Features : Semi Transparent Widgets, adaptive taskbar icons
For other looks/effects/how to use this theme - visit : https://github.com/rkstrdee/Arch
You'll need plasma 5.22 or above to enjoy full features like opaque/adaptive/translucent.
To enable Glass effect go to settings -> Desktop Effects -> uncheck "Background Contrast"
To disable Glass effect/change current theme go to settings -> Desktop Effects -> check "Background Contrast"
To get Clear Glass effect go to settings -> Desktop Effects -> uncheck "Blur"
To get rounded corners disable "Background Contrast", increase blur to increase text visibility.

Arch Kvantum theme
https://www.pling.com/p/1541674/