These days, AIBs really don't do all that much. In the past you had "enthusiast" cards with more RAM, dual GPUs on a single card, etc. but Nvidia cracked down hard on that stuff with (IIRC) the 10-series, which is also when they introduced the FE line.

Now, the AIBs differentiate themselves mostly on coolers, aesthetics (cooler design, RGB, PCB colors, etc.), and power delivery (though the latter is much less common).