You raise some good points Noggie, but I do think braking is slightly more dynamic than that.
Feel, bite and build at less full squeeze can change every day rideability and control.
Also, your ability to load the tyre steadily working up to 100% "ABS triggering" power can determine the overall effectiveness of your braking and impact braking distances.
And yes, tyres are as important as they transfer the forces to the road.
There are many factory for sure Phil.
Feel, how they bite, how they hold up when abused (temperature).
But ultimately, what actually stop you is the contact between the tire and the road.
I did a lot of track driving with cars when I was younger, the greatest difference between high performance pads and oem pads was how long they lasted on the track.
Oem pads would typically overheat and fade earlier, high performance ones would cope much better with abuse, however they wore out faster and tend to squeak more, and they made a lot more dust, and this burned into the wheels and stuck there.
My point was simply that in an emergency situation you step as hard as you can on that brake pedal, or squeeze that brake handle as hard as you can. At this point pads and rotors don't matter, your grip does, and that is determined by your tires, and road conditions.
But, as you point out, a brake upgrade can change your confidence in your brakes
I'm considering braided brake lines to get a better feel for the brakes, pads are not on my list yet, may upgrade when the oem ones are worn out, but I don't see the need to change then for the sake of changing them.