I forgot name of that committee. But there was a scene about it on Netflix's show The Last Kingdom, which was based on early middle age Wessex at the time of 7 English Kingdoms falling to Danish vikings and vikings start to be civilized although only a little. (Corresponds to 769 start?)
When King Alfred's brother, the former king was in death bed from a battle wound, he and all his councilors chose Alfred instead of his drunkard son. After the king died, power to choose the next king seemed to be clearly at the hand of that committee. When the former king's son claimed his right to the committee and lied that it was his his father will, a councilor replied that the next king will be selected by that committee and they will put the prince's claim on consideration. It seemed pretty clear that they would have chosen Alfred even if it was against the dying king's will, had lawful authority to do so, and clearly there was no fixed succession law like primogeniture.
By end of the show, now frail Alfred was in his deathbed after a few decades long and highly popular reign, it seemed clear that his son was already decided to be his heir either by a clearly set law or high crown power. The former king's son, a cousin of the new heir, wasn't even a real consideration if consideration against the king's wish was even a thing, which didn't look like.
The show also described Pagan's swearing fealty to a person, the king, and not the crown or the heir. The idea of game's tributaries breaking upon the ruler's death makes a lot of sense with that too. Wouldn't make any sense to serve anyone just because his father. Gavelkind in early age was more like Dothraki's, and the realm would be divided by its powerful commanders rather than underage children.