Now on one hand I tend to think that the first approach is valuable for many people but it does not seem to me to be for everyone..
The basic opinion of only Torah all day finds its basic expression in the Nefesh Hachaim of Chaim from Voloshin the major disciple of the Geon from Villna. But to a large degree it is implicit in older books of Musar and in the Talmud itself. In fact in the Tenach (the Hebrew Bible) we do find the idea that serving God is the only thing that has value. And in fact in a normal Lithuanian yeshiva we do find a basic kind of serving God. Though this is hard to put into words. You really have to have been there to have experienced what it is. The only way i can explain it is in the way that Gershom Sholem explains the evolution of ecstatic experience in the age of the prophets until the age of the kabalists. He sees the very experience itself as evolving and changing . While in the time of prophets we do not really know what they did to receive prophecy but we know they were not doing unifications. This changed by the time of Avraham Abulafia and Issac Luria, -the ecstatic experience because dependent on unifications.
The experience in a Lithuanian yeshiva is the direction that this experience has evolved to.
Unifications no longer bring the ecstatic experience, but rather a wide range of illusions.
The Shechina has set herself on Lithuanian Yeshivas.
However as I mentioned before this is not for everyone.
And to some degree we can see that many yeshivas themselves today have lost the touch of the divine.
While total immersion in Torah all day might good for some people but i have some questions if the Torah itself asks this from people. If we take a look for example at the first and foremost of all books of Musar --the Chovot Levavot [Duties of the Heart] we find that he claims [Shar Prishut] that one is obligated to learn an honest profession that does not include depending on being supported for learning Torah.
But in truth the idea of learning Torah as a profession i did not hear about when i was in NY yeshivas. There never was a question in anyones mind that one should learn Torah all the time but that it is not to be a paid profession. The idea in NY was that if one was sufficiently devoted to learning Torah that God would provide some means of support. in some kosher way--not in the form of a pay check for sitting learning.
Everyone knew the simple basic Halacha that one is not allowed to make the Torah into a device to make money. secular and religious Jews alike. Lakewood Yeshiva has attempted to scam people into thinking that learning Torah is a kosher paid profession. This is a scam and it is sad that some people have fallen for it. In Israel also the ultra religious have trying to scam the Israeli public about this issue.
There is a difficult fine line here--the line that one should learn Torah but that this should not be a paid profession.
Perhaps it should be noted the approach of Rebbi Nachman in this regard. To him Torah is everywhere. It is the root of all creation. The Ten statements of creation the root of creation and inside of them are the ten commandments which are to essence of the Torah.
Torah is everywhere and in all actions and in all people. But in forbidden actions the glory of God is not revealed. So how do forbidden actions have any existence? They is by the first of the ten statements of creation the hidden statement. This is the highest of all the statements. That means that when one has fallen into the kelipot-- areas of darkness where there is no glory of God and from there one realizes how far he is as fallen and begins to seek god from there, that is when he has the highest flight into the highest mountain.
The point being that one needs to learn Torah in order to find God. But when one does learn Torah and keeps his commandments then he can serve God through anything.