Those are excellent questions.
Out of the box my BG2 shot low-left at 4 yards on first range day. The hole closest to the bullseye is a POA at 2 O'clock. I had the “know-it-all” armorer look at it. He said “I guarantee it’s all you, and the sights don’t look that for off”.
This Saturday is a range day and I will bench test it.
Regarding the rear sight slot... this handgun is marketed as a pocket carry for self-defense at a close encounter of the worst kind. I prefer a green painted front sight. The glow-in-the-dark green tritium for targeting in the dark is a non-issue for me. If I have to shoot in the dark, I’m not going to be looking at the front sight.
I assume S&W’s thinking is that the larger-than-desired slot in the rear sight aids in locating the front sight quicker during SD situation.
The problem with the rear sight is I can’t find it quick enough. Before I install the new XS Sights, with bright white fingernail polish, I painted it. It’s better, but I prefer the white dots on the XS Sights.
For fun at the range, the XS Sights should make you look like an expert hole-punching dude at 7 yards. In reality, if I have to shoot during an SD situation, I probably won’t even see the sights. According to all the experts, it will most likely be a point and shoot pew pew.