To soften a strap, I simply roll it back and forth lengthwise a few times to speed up the time it takes for the leather to conform to my wrist. No elaborate rituals.
I also purchased a dark green strap from them for my Evo. I had been wearing a burgundy red strap that came with the watch, which I really like. But the dark green is richer looking.
You are absolutely correct about the difference in watches. Even though the lug width is the same, I couldn't see putting either of the Breitling straps on the Chopard, nor either of the straps that I boutght for the Chopard on the Breitling. I can't speak to the IWCs, though.