Qt for Python (PySide/Shiboken)

Maybe not a true Python question but closely related to the bottle necks in QML. I have experienced before that QML has some limitions when doing processing heavy image and video stuff. Together with the original single thread nature of Python I did many workarounds before. Now exists the (wayland) compositor. Considering I control all the hardware myself. Would there be a benefit of running independent proces-es on top of the compositor. Or should running the entire thing in a single application be 'better'. Practically I typically benchmark the behavior of the GUI using a marquee style element where I expect that that marquee is completely stable and stutter free. I have noticed before that running this is a dedicated application is much more stable than being part of a bigger application.