Unfortunately for now I'm not able to tell you what is causing this issue. It can be some inefficiency in the Qt library itself or some compatibility issue on your computer.
I'm not fully aware of how Nvidia drivers as the same as
mutter-x11-frames working with Qt.
Isn't possible that this
mutter-x11-frames process is shared across multiple processes for example?
Anyway, unfortunately, there is not much more that we can do. We're not working with Nvidia drivers directly, we're using Qt libraries for GUI access, and the model is generated/drawn on Canvas also via Qt.
I would like to fix it and help you more, but for now, I'm not sure how.