These words refer to two different kinds of touch feelings. In view of my experience, 烫 is deeper than 热. You will get hurt by the 烫 without any prevention. You may be hurt by the热, and however, the 热 can also refers to a heat you can take. And I think those two sentences you asked can both be used. The keyis that the adjective 很. I assume that they are similar to each other with the 很. For reference only.