In developer options of my phone I enabled GPU profiler, and Webview seems detached from directly getting touch screen input and works very well like Opera mini is smooth.
Samsung browser has a detached from touchscreen directly like GPU profile too.
Communicating touchscreen events directly to Opera or Chrome main thread that is also the viewport seems to be culprit here.
I suggest Opera developers to try a simple overlay window that passes touch events forward to the web viewport in NDK since directly communicating with NDK is problematic. Not only for Opera but for Yandex, Chrome, Brave browsers...
Opera could do this as Opera Dev version e.g.
I turned almost into Steve Jobs.