Opinions please on CLASS H amplifier

As the others have already said, class G and class H are class A/B. Or class A if the output stage is A. Or class B if the output stage is B.

Suppose you have a class A amp. You can turn it into a class G amp by adding a second power supply and a circuit to switch from one supply to the other. That’s it. The output stage would be identical in both cases. The only difference is that it switches to a higher power supply when the signal demands it. IOW, you get the best of both worlds — the output stage you want and the improved efficiency.

But azn is right — there are many other things that can make one amp better than the other that you can’t predict from the class.