No, that is why I am asking. When you render to the PV the Octane settings in the C4D render settings are used.
In the first tab there is a "Use all GPUs" setting that is enabled by default. So when you render in the Live Viewer Octane uses the Octane settings and uses only one GPU.
But when you render to the PV and "Use all GPUs" is checked it overrides the settings in the Octane settings.