Haha that's a very tricky question! You have to slice it into different situations:
1. While the ABS is active, all 4 wheels will be at their maximum braking. That's like a dynamically changing, front/rear/left/right brake bias. No, brake bias won't make ANY difference. It's overwritten by the ABS
2. While not braking hard enough for the ABS to kick in, the brake bias will make a difference! Like fast corners where you only touch the brakes slightly or while letting off the brake pedal when starting to turn in for a corner
How
I do it: It's always good to know what the actual capabilities of the car are so I always do some laps without ABS and without TC, driving quite carefully, trying to get used to it. How to go off the brake pedal for a nice turn in, how far you actually can press the brake pedal before the tires will lock up. How brutally you can put your foot down on the throttle at corner exit etc.
After you're used to the car like that, and adjusted the brake bias, I put ABS and TC back on and of course you will be a lot faster most of the times! But your feet will still move "according to the car's capabilities".
An example: I often see people, when driving with ABS, mashing the brake pedal until they start to turn in and then just letting it go, resulting in an unstable car.
Now if you try to do the same without ABS the wheel would just lock and then snap back into grip.
However when you can drive the car without ABS and then put it back on, you'll be very smooth, and therefore quicker!
To answer the question about the brake bias: yes, set it. But set it while driving without ABS please