Vlad
Disabling favorites helps significantly but does not completely solve the issue. Displaying frequently visited sites on start page still has some minor stuttering and white artefacts when swiping between two start page tabs.
Disabling both favorites and frequently visited (i.e. having a completely blank start page) still has the white flashes issue but otherwise the swiping is smooth.
Video of just favorites enabled:
Video of frequently visited enabled:
Video of having a blank start page: