In my tradition (Triratna) there is a big emphasis of a lot of samatha practice before any vipassana practice. This has always made sense to me. However is this universal in all Buddhist schools? Are there any Buddhist schools that do minimal or even no samatha practice? Does anyone jump straight into vipassana?
While different traditions might emphasize one over the other, they all need a certain level of development for both:
"These two qualities have a share in clear knowing. Which two? Tranquillity (samatha) & insight (vipassana). "When tranquillity is developed, what purpose does it serve? The mind is developed. And when the mind is developed, what purpose does it serve? Passion is abandoned. "When insight is developed, what purpose does it serve? Discernment is developed. And when discernment is developed, what purpose does it serve? Ignorance is abandoned. "Defiled by passion, the mind is not released. Defiled by ignorance, discernment does not develop. Thus from the fading of passion is there awareness-release. From the fading of ignorance is there discernment-release." AN 2.30
About the order of development, it could be in any order:
"There is the case where a monk has developed insight preceded by tranquillity...Then there is the case where a monk has developed tranquillity preceded by insight...Then there is the case where a monk has developed tranquillity in tandem with insight" AN 4.170
Often mediators will get stuck in Samatha thinking that they have become permanently enlightened. Samatha takes away all the defilments but it's only temporary. Also mediators could get addicted to the bliss and calm that samatha brings. So, yes there is vipassana only approaches called "dry insight meditation" like in the Mahasi tradition that is perfect for laypeople and monastics.
You should not have an emphasis on which should develop fist but let it take its natural course. Both are important as wisdoms has concentration as the base and concentration has morality as the base. Like a roof over your head cannot exist without walls and a foundation.
Well, according to AN 9.44 PannaVimutta Sutta Doing Samatha-Vipassana at the same time is the best way to Obtain and realizing Wisdom.
Without getting into Jhana, it would be hard to grab the true meaning of dhamma. As you get deeper in Jhana, your level of understanding will help you to understand the true meaning of dhamma.
As for AN 4.170 Yuganaddha Sutta, You need to read from AN 4.162-169 to understand more about the differences between each methods.
The best way for the human in this era is Samatha-Vipassana.
Without any previous concentration exercises or Samatha training, no Insight is possible. How can you register the different sensations which arise and pass away so fast without a sharpened concentration? Anapanasati as a concentration exercise is just one of many. Walking, being aware of the movements of the feet is concentration. The Mahasi method of labeling the stretching of an arm is concentration.If you enter for a while into a deep jhana, nothing wrong. Enjoy it. Later it turns into a sober concentration and becomes normal. Very naturally one slips into Insight meditation.