1. I carry 230gr FMJ or LRN, when I carry the pistol. JHPs are fine, but they are probably a waste in anything heavier than 200gr, since the velocity is much lower. Most studies that I have seen show that the 200gr JHP is the optimal load.
2. Grain weight affects velocity and point of impact. Higher weight = lower velocity. Higher weight = higher point of impact. The CZ 97B is "designed" for the 230gr weight in the sense that the fixed sights are registered for this bullet weight. Lighter bullets will shoot lower with the OEM sights.
3. The theory behind +P is that the higher pressure (+P) allows for higher velocities. Once again, +P loadings make more sense in the 185gr and 200gr bullet weights. 230gr loads do not greatly increase in velocity, as compared to the lighter bullets. The CZ 97B can handle +P loads, but I would suggest at least a 16# Wolff spring.
In theory, a 200gr +P JHP would be the best defensive load for the pistol. In practice, the big and slow 230gr load is a bit more accurate.