OK, sure.
The Baal HaTanya explains that when you do a mitzvah in the physical world, you are taking something which is part of the kelipos (k’klipas nogah) and elevating it to Kedushah. On a simple level, this is because this item appears (to us) as separate and distinct from HKB”H, and it can be used for any matter of things which is not for Avodas Hashem. By using it for Avodas Hashem, that item is raised to Kedushah. The mitzvos, in general, are rooted at a higher level in the סדר השתלשלות than לימוד התורה.
Nevertheless, the mitzvos are compared to a levush for your neshama, and learning Torah is compared to מזון for your neshama. מזון goes to the inside, into the פנימיות, while the mitzvos, even though they are rooted in a higher place, only go to the חיצוניות of the neshama. [As with many things in Chassidus and Kaballah, you will find over and over again that it is wrong to ask the question, “which is on a higher level of kedushah?” Generally speaking, each has a מעלה that the other does not have].
The יסוד of limud hatorah going into the פנימיות of your neshama is based on the idea that it is the פירוש of the mitzvos (i.e. the peirush is the פנימיות). This is discussed at length in Torah Or and other places. A good starting point would be תורה אור ד”ה יביאו לבוש מלכות.
Anyway, this reasoning is not relevant to קבלה in the same way as nigleh. on a deep level, kaballah is meant to add a neshama to your avodas Hashem, not to explain the mitzvos. As a result, Reb. Aharon Strusele explains in his seforim that I discussed above that the idea that Torah is מזון לנשמה only applies to nigleh, not his seforim. As a result, he specifies that the main limud should be nigleh, not nistar.
I hope that this was somewhat understandable in the way I explained it.
That being said, different people have different שרשי הנשמה and as a result, they have different חלקים in Torah. I myself can DEFINITELY relate to Chabad’s desire to spend the day learning Chassidus, as this brings one extremely close to Hashem in a different way than regular limud torah. That’s why I said earlier that everybody needs to find a balance for himself. Even a person whose שרש הנשמה requires more chassidus and/or kaballah still needs to learn nigleh. And I definitely disagree with a blanket rule that one should only learn it for a half an hour a day.
One Rav who I am close to, who was the first person I learned שער היחוד ואמונה with, suggested that perhaps 2/3 nigleh and 1/3 nistar, and this has always felt like a good balance to me.