powerdvd would always use the GPU which is in chrage of the main display if you are using a laptop, and the GPU is usually the Intel one if your latop has hybrid GPUs.
I'm not sure what symtom you exactly encountered when using "Power saving mode" with PowerDVD and how powerdvd forced you to leave power saving mode. An integrated Intel GPU is much more power-saving versus discrete AMD or NVIDIA GPU.
Anyway, "Power saving" mode might interrupt many normal processes regarding the DRM video (e.g. commercial Blu-ray movie) playback, and it does not have such universal industry standard for what the power saving mode should optimize or not, but totally depends on how the PC, laptop manufacturer, or software manfacturer implements.
No surprise IF a power saving mode would cause some normal playback functions not work.
Ask the vendor that ships the power saving mode features in their hardware for help.
No need to mention that there are many malware disguise themselves as battery saver or calibration tool.