As for the so-called rough breathing, I'm sure that this [h] sound was not an undroppable consonant in ancient Greek. As a matter of fact, the English [h] sound is often dropped or elided in normal speech, as in "I know that he has his book."
Ancient Greek, I believe, originally wrote the [h] sound as in Latin and English, but then later went to the sign that looks like a backward apostrophe. Why? I believe that it was not a consonant that was always pronounced, but was an onset to an initial vowel.
The so-called "smooth breathing" is a glottal stop, by linguists called a "rough onset." Now, a glottal stop is heard before a vowel at the beginning of a breath group in English, Greek, etc. But if other sounds precede, you don't always hear the glottal stop. That's why we say "a book" but "an apple," because the glottal stop at the beginning of the word "apple" is generally elided if anotheer sound precedes. I say generally, because in child language you can sometimes hear a glottal stop instead of the n: "This is a 'apple."
By the way, the so-called "rough breathing" is called by linguists a "smooth onset." In other words, instead of pronouncing that glottal stop before an initial vowel, you aspirate an [h] sound before it.
Now, some words in ancient Greek change depending on whether a vowel or a consonant follows. An example is the word ek/ex (εκ/εξ). It's common knowledge that ek (ἐκ) precedes a consonant, and ex (ἐξ) precedes a vowel. But notice: It doesn't matter whether the word following ek/ex (ἐκ/ἐξ) has "rough" or "smooth breathing"--it still begins with a vowel! Now, if the "rough breathing" were an undroppable consonant, it would doubtlessly have ek (ἐκ) and not ex (ἐξ) before it--but in every case ex (ἐξ)--and not ek (ἐκ)--precedes a vowel with "rough breathing."
Also, within a word here is no [h] sound. That's probably another reason the Greeks stopped writing the letter h andjust started writing a vowel with one or the other of those apostrophes, "breath marks."
After reading the Greek New Testament (and also some classical Greek) for many years, I became convinced that the [h] sound was not heard if another sound--vowel or consonant--preceded it. So if a word begins with a vowel with "rough breathing," if I pause before that word, i.e., the word with an initial vowel begins a breath group, I pronounce the [h] sound. But if, on the other hand, I make no pause between a preceding word and a word that begins with "rough breathing," I don't pronounce the [h] sound any more than I pronounce a glottal stop in such a case befor a word that begins with a vowel but has something before it.
I hope this makes sense. The text of ancient Greek screams it at me, i.e., the "breath marks" have to do with the onset to a vowel in initial position at the beginning of a breath group. Neither the glottal stop of the "smooth breathing" nor the aspiration of the "rough breathing" is something that is always heard.