That second gen feistiness seems to happen with carni’s as well. My overwintered hive queen was from a carniolan swarm cell and they get worked up very easy. I’ve been stung 5 times by that hive this season, and only once from my 12 other new hives.
Some of them are very persistent as well. If I’m doing a full inspection I suit up completely knowing they are going to get worked up. During my mite counts a few weeks ago I was in full suit including long gloves and one of them managed to get in under the glove and sting the back of my hand inside the glove.
On the original topic of buckfast vs carniolan I currently have both, and after a year with them can’t see a big difference. Both seem to build up strong colonies quickly, build beautiful comb honey, and are very gentle. It will be interesting to see how they perform through the winter here.