I'm sure everything I'm about to say has been said here, but I've been riding those brakes almost 60 years. 80,000 miles (plus 30,000 miles on Mafac cantilevers of the similar vintage).

Those RACERs are famous for the squeal. When the pads were new (and young), stopping power was simply excellent; even if bystanders had to cover their ears. Tweaking calipers for toe-in? We all did it and those of us who rode MAFACs are still alive (or passed from other causes). I used to try to optimize squeal for low volume on routine stops and howling with a powerful front brake lever grab. Very useful tool for Boston traffic. When a driver pulled a careless or a**hole move on me, I'd hit that front brake, sit up and point to the car. Every pair of eyes for a block around turns to look at me, then follows my point to the driver. Driver comes out of his stupor and realizes everybody is looking him! Driver slinks off like a guilty cat. It was pretty funny.

KoolStop came into existence as the original MAFAC pads were hardening beyond good. (Thank you, KoolStop!) They work with considerably less squeal. Really good pads and work superbly with all the Mafac brakes. They come in black, salmon (a brick red) and a mix of the two. The salmons are the best pads out there if you want to stop in the wet going down a very steep hill but they pick up a lot of road grit and so can wear rim sidewalls fast. The black pads are excellent dry road pads and OK in the wet but not great. The mix is in between. I'd use the pads that best match your average riding. I live in Portland, OR and ride the black on an old race bike that has no business being out there in the wet, the mix on my good bikes and the salmons on my rain/winter/city bikes.