I sense that this might be concluding so I am going to share my very limited experience. I have a 1993 NA Supra and a 2003 Lexus GS430. For the Supra, I recently had all four calipers refurbished and replaced all four discs and flexible hoses plus a change of fluid.
I was horrified by the condition of the calipers before refurb but I hadn't noticed any lack of braking in normal driving. As far as I know, the Lexus shares a very similar brake set up to the Supra. This is despite the Lexus surely being much heavier and considerably more powerful. You would expect that Lexus had fitted at least adequate brakes as standard. My current car and one that I drove new years ago, both give the distinct impression that you could arrive at a corner travelling too fast for the brakes to save you from the hedge or worse. This is probably a perception as opposed to reality, but I certainly felt it. My solution for the Lexus has been to fit lowering springs and Supra Turbo front brakes. This solved my issues with the car without a dramatic difference in any aspect of performance. My feeling is that the springs reduced the diving under braking and wallowing into corners. In normal road driving the assumed greater braking performance is probably more in the mind than anything, but it's still nice to have. I should say that the front discs and lower ball joints needed replacing so it seemed to make sense to do the additional work at the same time. Of course I'm now slightly worried that I should be upgrading the rear brakes. I'm going to be leaving the Supra brakes alone now but do plan to take it on a track day soon.