I have only been keeping them for about 6 years. I've observed and admired them my whole life. I got to know them when I was a kid. I followed them and would regularly find feral hives around the neighborhood I grew up in. There was a massive hive in a 400 year old eucalyptus planted by the Spanish conquistadors. That hive was there for at least a decade.
The size of the bees is not dictated by genetics entirely and has a lot to do with the size of the cells that the bees choose to make. The older the brood combs get the smaller the bees generally get. There will usually be a good variation in sizes with most feral colonies. Big bodies are pretty common for euro dark bees.
Do they have silver or gold hair? Are they sunset colored underneath like coppery or are the black ones black all the way around.
There are people working to replenish the grey/silver Caucasians in the Appalachian region. All the feral bees here have a lot of genetics going on, black ones, striped ones, fuzzy ones, gold ones, all in the same bunch. This state has some of the oldest bee genetics in North America still in it's feral colonies.
I'm very happy that the earth blessed you with some swarms this year. Congrats. It feels so good when that happens. Mean bees are often survivor bees.