Better wouldn’t necessarily be the right qualifier, but faster, typically more repeatable, and greatly more economical with scale/workload would certainly fit as better from different vantages.
With high novelty? Probably not until machine learning and compilers are deeply entangled.
That very much depends on the code. Program synthesis is an active area of research and the programs found would often be very difficult for a human to figure out. Of course a sufficiently determined human can always do whatever these programs do, but I do think it is unfair to give an unlimited amount of time to human optimizers.
With high novelty? Probably not until machine learning and compilers are deeply entangled.