Very differently. The most extreme case was Carlos II, king of Spain, of course. However, part of the question depends on the reason for the bite. In my mind, open bite might affect speech more than progenia. But sometimes larger lower jaw might be associated with acromegaly, and then the tongue might be enlarged, and this makes speech unclear. On the other hand, Jay Leno has prominent lower jaw. I don’t remember how he speaks, but judging by his career, should be distinct?