Top load.
I already have a subtle, delicate "wood matters" kind of bass. That one is super-sensitive to minor changes in setup or technique. I bought the ATK because I needed a bratty, active-EQ, take-no-prisoners-dime-the-treble rock and roll instrument, to round out my rig.
That said, I didn't hear a useful difference when I tried string-through on other basses. I'd expect the same and more on the ATK, because of the thick finish and the truly massive bridge plate. It's just not the woody, sensitive type, at least to my ears. Besides, if I acknowledged that string-through might make a useful difference, then I'd be forced to bust the body out of its polyester straightjacket and eliminate the '57 Buick chrome bridge, just to see what happened. Frankly, I like the ATK just fine as it is, and don't want to invest the time and effort on a strip and refin.
I bought this one to play, not to obsess over.