Malcolm Own at Apple Insider has an article on M1 Pro and M1 Max GPU performance versus Nvidia and AMD.
Now it uses teraflops to compare it to what the equivalent processor is, meaning the top of the line is equivalent to a Radeon RX Vega 56 or GeForce RTX 2080.
Which also means my Radeon Pro Vega 64x, which can do a bout 13.5 teraflops (12.5 teraflows for the 64) is still better, but still slower than a RTX 3060 Ti or above processor.