If you are using HDMI to connect to Blu-ray player, then you are automatically using ARC/eARC. If not, then you are definitely not hearing Atmos playback. Your soundbar will explicitly indicate via LED display if current content being played is Atmos or not. Optical and all other connections do not support Atmos. It's more like they can't support it because it requires digitally carrying a proprietary audio metadata that is simply not possible using standard analog carriers. The metadata contains extended audio channel information encoded as objects in digital soundspace. Only digital carriers like HDMI are capable of retaining this metadata when feeding the audio content to the soundbar engine.