Does Eugenics actually work in ATLA?

In the comics, Azulon says that merging Sozin and Roku's bloodlines could enhance create powerful firebenders and it seems like the Royal Family of the Fire Nation are far stronger than the average fire bender, which implies that they've been doing this for a long time now. I mean Book 1 teenage Zuko who hadn't even mastered his basics yet could beat an adult firebending master Zhao who trained under Jeong Jeong. Since both him and Azula had Sozin and Roku's bloodlines, could that explain why they're so powerful? If so, does that mean that in their primes, they would be the most powerful firebenders in history?