I have not owned a .223 Vepr myself yet, so I'm just going off of my knowledge of the other calibers I do own, and the other .223 Veprs that are owned by my friends. (there are a lot of them around here, but it is a local company).
I don't know the twist rate on the .223. It probably says it on the webpage. I seem to recall 1/9, but I'm not sure on that.
The trigger parts interchange with a regular AK.
Twoblink, I'm actually not that good of a pure accuracy/bench rest shooter. I lack the patience. My tastes run more towards 3gun than bench rest. So lots of rounds with decent accuracy fast.
In somebody like Steve Smith's hands, then you see what real accuracy is. Me, I'm just average.
The stock sights do not lend themselves to real good accuracy, since they are standard AK buckhorns. I hate buckhorns. I'm running Krebs A2 dustcover sights now for irons. Much nicer.
Twoblink, really you are going to need to get your hands on one to play with to see how it fits you. It is a heavy gun, and it feels a whole lot different than the M1 Carbine. I'm assuming from these recent threads that you are coming back to the states soon. This is definately a gun you need to play with first before ordering.
However if it fits you, I can't recommend them highly enough. I really like mine.