We call yellow bees italians . They are over the world, and they are so many kind. And crossed many ways. The color is no measure for good queen. As you reed Susan Cobey's wanted features, it takes number of generations to pack all features purely to one animal. And many have tried before her.
When we have experiences from Italians, they will be many and confusing, because they have plenty of variations.
There are several strains. Swarming is natural to bees. If you take queens from swarmed hive, it is probable that it make swarms next summer. If you take from angry, you get anry daughter. Angrynes and will of defence are also natural features. - Don't take them personally
Also if you take care different way like the queen raiser, bee response any more that way like queen raiser wanted.
15 years I have byed a couple of queens from professional queen raisers and then I have taken larvas from them and raised own queens, but only one generation.
I am satisfied with results. I have not byed hybrides, because it does not work any more if I take daughters F2.
If you want good wintering bees, bye the queens from north, 500 or 1000 km away.
I have too little hives to get one good mother to my own queens. It works better with professional beekeeper,who takee the best from 500 hives than I take the best from 10.