Icons in the notification area cannot be changed easily. You would need to edit the actual icon as root in user space with an image editor. The chromium theme simply uses the GTK theme I designed. I cannot remember what else I did with it. To avoid screen tearing, you may need to install a proprietary driver and then use the fixes at the driver level using their control center. The Manjaro hardware setting tool will give you the option to automatically install the driver you need.