Reckon the crossover settings are for the TV's speakers.I am getting a Panasonic 65GZ1000 OLED on Friday. It comes with a subwoofer out and crossover settings. Going to see if the TV is able to send sub out sounds correctly. If this does the trick then time to get keep the LG sub at bay and use the dedicated active sub.
When you set the soundbar as the audio source, it will disable all TV audio.
Does that TV do eArc?