As for Server-Client differences between JPs and NAs, JPs may have a slight advantage on average, but the latency between your computer receiving the information and displaying it is large enough that it doesn't matter as much as you might think. By and large, I've always felt this is just a crutch NAs lean on when they're outclaimed. JPs use the same excuse.

When you use the <stnpc> "macro", the cursor is already out before the ??? spawns and will default to the ??? when it spawns if you do it right. It's really just a matter of how quickly you detect the change and hit X/Enter, or your reflex time. I very very rarely get outclaimed using this method. /targetnpc would literally have to target it before it spawned to be better than this.