Note that the Point-Defense Ship design type only exists in a couple of mods and not in the stock game.
In response to your earlier question, It's more or less like SE4, in that your PD ship needs to have at least 1 offensive weapon. Targeting priorities rule the day when it comes to actually trying to control what you fire at, but in most cases with PD, it's firing at the first target it acquires. You can fool around with the % targeted damage settings to see if you can get better PD splitting.