Also this one from ten years ago: https://bitcoin.stackexchange.com/questions/28392/gpu-mining-strategies-algorithm
Good question from four years ago, anyone know the answer? https://bitcoin.stackexchange.com/q/100221/4948
Discussion
The second question is basically what made GPU mining more efficient than CPU mining. The existing answers suggests part of the answer is unknown, because there's proprietary manufacturer code involved.
The first question is about whether GPU can still be useful for the remaining sha256 usage in block validation. My guess is no because CPU specialized instructions are good enough for that.
But if the answer is yes, maybe on Apple Silicon with its shared GPU & CPU memory, maybe there's still some opportunity?
I have no idea. Useful to document.