You will find a world of different information with regard to various races of bees and the hives they are kept in. Note that B+ keeps his Carni's in double Langstroth's. The reason being that a single is not enough for a prolific queen, especially in the spring buildup.
My suggestion is to determine which bee to keep based on local flows. Here are a few generalizations worth considering.
Carniolans are adapted to areas with strong spring and relatively weak fall flows. If this describes your conditions, then they will perform as well or better than other races.
Italians tend to brood up starting in the spring and maintaining a large colony all summer and into the fall and overwintering with a large cluster. In my area, that huge colony in mid-summer and all winter is a huge detriment. Italians can be really good honey producers, but my experience is that their wintering ability is not good enough.
The A.M.m. colonies I've worked with would build up very strong in the spring, then curtail brood rearing during the summer, and increase numbers again for the fall flows. Their weakness is a very strong tendency to swarm and a tendency to collect honeydew in preference to floral honey. Their incredible vitality and ability to survive with very small colonies over winter make them acceptable in some areas. I won't use them because of issues with the honey produced.
Buckfast have to be given consideration, especially if you have a strong spring flow and another strong fall flow. They can easily fill a double Langstroth with bees and brood. I can use Buckfast to good effect with the flows and conditions under which I keep bees.
Caucasian's have advantages in areas with long slow spring buildup and especially when the fall flow is very strong. I won't use them because they fall short in the spring flow. They are also inveterate propolis hoarders gumming up every interior surface with sticky goo.
From the description of your region, Carniolans and Buckfast should be primary contenders.
So what bees do I keep? My bees are mutts from crossing A.M.m. with Italians and with a bit of Africanized genetics tossed in. I have not treated for varroa since the winter of 2004/2005. My bees exhibit strong hygienic behavior with a dose of hive beetle resistance from the Africanized genes. I have little or no problem managing them as I culled the worst stingers and kept the bees that could be worked while wearing a t-shirt and jeans. My current breeding project is to raise queens from 2nd generation Buckfast and mate them back to drones from my line. I'm getting very gentle bees with excellent honey production, zero issues with varroa, and good control of hive beetles.
Amazing how much knowledge we have tucked away collectively, thank you very much.
