The AFL really never existed as a real football competitor of the NFL before the first SB. They were really not as good as the NFL until the actual merger in 1970.
Top to bottom, they were inferior to the NFL.
My point is that the NFL championship before the suberbowl was the championship of the best teams and players in the world. The Superbowl started before the AFL was really anywhere near as good as the NFL.
In other words, there was never any "sub championship" or anything close to it before the SB era. The NFL chamionship was the true championship of pro football.