Can a 20km torp Shima even strike something if those torps are ungodly visible?
Yes, her own allies. Although these days it does nothing, and it was more of Yoshino's thing. Back in my days.... They are more of a double noob trap. One because a player took them in the first place, other noob goes: "Oh they were detected 10km away, they are about to run out anyway, why dodge?"