Lawyer here, but this comment is not legal advice and you should not act based on it.

You're right in the sense that restrictions on how and when one can speak are viewed differently from restrictions on what sorts of things people can say (the later are virtually always unconstitutional, where the former are constitutional under certain circumstances).

But this doesn't boil down to a difference between expression and speech. The Constitution never mentions freedom of expression, merely speech, but they can be talked about relatively interchangably. The important part for both is usually that the government cannot regulate on the basis of the content (e.g., no talking about war) and especially not viewpoint (e.g., no supporting war). There are exceptions and nuances, such as reasonable time, place, and manner restrictions in some circumstances. Your example in another comment of restricting negative speech to a cornfield in Iowa would be unconstitutional, but preventing people from blaring loudspeakers at 4AM would be fine.