I think the Bills have been most successful when Josh improvises: He can buy enough time for coverage to fall apart, and then he can throw a dart to anywhere, from any position. It's a huge advantage, albeit a very unpredictable one.
Unfortunately, he is not nearly as good at hitting the planned quick reads over and over again the way Brady did. If he ever figures that out, and I think he can, he could be the GOAT. He just needs to process the first two seconds of the play a lot faster.