You are talking about a throughput part of problem only not even a word about latency. If you are going to not think about what finger will press "A" key then y

You are talking about a throughput part of problem only not even a word about latency. If you are going to not think about what finger will press "A" key then your brain the bottleneck is going to be less like a bottleneck. Not touchtyping while typing means misusing your limited neocortex resources instead of just utilizing your muscle memory.