I think this thread explains it. Probably applicable to the 502vs as well.*https://rog.asus.com/forum/showthread.php?104886-GL702VS-power-supply-adapter-charger-very-underpowe...
I experience exactly what the OP describes in this post and I can confirm 100% my cpu/gpu are well under control with both being undervote.*
230w AC adapter for the 502VS/K should be enough. Mine runs absolutely fine with it, but I have to admit I'm curious to see what a more powerful AC adapter would do (probably nothing in this case, tbh). GPU hits power limit at 1840mhz/0.875mv but that's limited by the EC chip.
Now, if you have the first revision of the gl502vs with the 180w AC adapter, then yes you should get the 230w one and update your BIOS if you haven't yet. They added support for the more powerful AC adapter and tweaked some other stuff, as far as I know.