Hey, thanks for the elaborate answer !
It's true, the initial days of retreat can be challenging to flow through. In fact, what I have noticed is
It only keeps getting harder for me, the last 3 days being the toughest except for the last one where we are allowed to talk. I usually count the days left to reassure myself it's not long before "freedom". Maybe because I just started little less than a year ago, my ego is still very strong and keeps revolting every time an attempt is made to dilute it. I agree that someone with decent knowledge of physical postures would be able to calm down and accept things the way they are rather than fighting everything, and get into an overall more conductive mood.
Yogic and buddhist meditation practices are both amazing. Somewhere I was reading (maybe "Heart of Yoga" or "Tree of Yoga") that some yoga practitioners specifically send their students to buddhist teachers to learn the meditational training on emptiness (no self, no thingness), but they wait till their students have finished raising their families and finished their careers out of concern that the realization in emptiness may take the gumption for work and responsibility and family ties out of their students.
Well said.
Being raised in India I know that lot of family people/householders do basic Yoga postures/breathing and achieve physical benefits from it. It doesn't influence the flow of life and people can go on doing whatever they are doing, usually with more enthusiasm, energy, etc. In ancient India it was the tradition that once someone became a grand parent, they could dedicate their remaining life entirely towards spiritual growth. Some would even renounce altogether to live in forests as hermits.
Vipassana (in pure form), on the other hand, is more like a mixed bag. Different people go through different degrees of experiences over a relatively short or long period that can have massive or minimal influence on their lives. It's a practical approach and directly works on eliminating Sankharas without any poetic explanations or mythology. Maybe a strong and disciplined practice controls the adverse effects such as viewing everything as mundane and even finding emptiness in baisc pleasures (which in my knowledge is not a popular consequence of asanas). This can even lead a practitioner to forsake worldly life altogether and become a monk, which may or may not be a bad thing depending on how you look at it.
Yoga is actually a loose term for a very diverse range of techniques, and "Asanas" are a small part of it. Asanas are a small component of this huge and diverse system. The underlying belief about Yogasanas is that by developing complete mastery over the physical form, one also develops mastery over the mind and eventually achieves "divine union", or Moksha.
There is a book called "Kala Bhairava Tantra" which lists over a 100 techniques, including Anapanasati and possibly also Vipassana (I only read through a dozen or so). As you rightly put it, the mental aspects are the Mantras, Sounds, Visualizations, Breath manipulation, Devotion, Beliefs, etc. According to Goenkaji, these practices are very effective at working on the conscious mind, but they do not effectively address the very root of the problem of clearing out Vikaras/Sankharas from the subconscious mind. The beautiful thing about Vipassana is it is only a constant effort to see whatever is there in the moment.
About pranayama: so some buddhist meditation teachers apply specific breathing techniques: there's bamboo breathing from Sekita in the zen tradition, for example. This technique can help a person stay awake, it can also be a massive distraction. So, you're right (in my view): special breathing is not done. Personally, I think this is because part of the utility of passing through a tremendously drowsy mental state on the cushion (say around the 30-45 minute mark on the cushion during the first few days of retreat) is that when the mind snaps to attention after that drowsy state, some serious training has occurred: The body and brain are learning that pure will power/intention is boss for the next few days at least.
According to Goenkaji, the natural breath penetrates at the deepest level of the subconscious mind. This is why our moods/emotions are reflected in our breath pattern. When we control our breath, we are creating an artificial mental state on the surface level while ignoring the problem at the root level. The mystical syllables are also artificial vibrations that can be introduced to calm down quickly. Observing the natural breath is obviously also more difficult than other techniques, because it goes so deep. In the Goenka retreats as well, when we are sailing through rough waters (or when unable to focus on natural breath), we are instructed to breathe slightly harder than the natural breath. It is easier than watching and helps to stabilize us a bit. Then we can go back to the natural breath.
Swimming used to be my favorite activity before I lost interest in exercise altogether. This is why I'm looking at Yoga. I feel that the slightly mood stimulating effect of Yoga will keep me hooked.