I haven’t seen those theories before. The first one seems intuitively apt.

If you are overwhelmed the first thing that goes is your leisure and creativity. Say if you used to play piano or did any hobby, and you stopped, it means you lacking bandwidth to relax. After that, and you don’t correct your brain starts changing until it breaks : a burn out, or even further along : PTSD.

So to counter it, is to bring back leisure and your hobbies.

If someone burns out right next to you (I have had that happen to a colleague) is a couple of things : you can ask them if possible to focus on deep breaths, or ask them to call out the name of objects and ask them to describe them. Another strategy is deprive them of sensory overload. Have them put the hands on their face and hunch over so they are in their own cocoon. Stay with them and soothe them until you get a professional over.

I am not sure if this is the most current view, but this is from my direct experience.

This is good advice. One thing to note is that deep breathing needs to be slow. If you over oxygenate you may get weird sensations which can cause more anxiety. The standard advice seems to be 'square breathing': In for count of four, hold count of four, out for count of four, hold again for four.

Sensory overload sounds specific to some neuro divergent conditions, might not help with other people.

This excerpt has resonated deeply:

But, parallel to this political phenomenon, we observe the disappearance of free time. Free space and free time are now just memories. The free time in question is not leisure as commonly understood. Apparent leisure still exists, and even this apparent leisure defends itself and becomes more widespread through legal measures and mechanical improvements against the conquest of hours by activity.

Workdays are measured and their hours counted by law. But I say that inner leisure, which is something entirely different from chronometric leisure, is being lost. We are losing that essential peace in the depths of our being, that priceless absence, during which the most delicate elements of life refresh and comfort themselves, during which being, in a way, cleanses itself of past and future, of present consciousness, of suspended obligations and ambushed expectations. No worry, no tomorrow, no internal pressure; but a kind of rest in absence, a beneficial vacancy, which returns the mind to its own freedom. It then concerns itself only with itself. It is freed from its duties toward practical knowledge and unburdened from the care of immediate things: it can produce pure formations like crystals. But now the rigor, tension, and rush of our modern existence disturb or squander this precious rest. Look within yourself and around you! The progress of insomnia is remarkable and follows exactly all other forms of progress.

How many people in the world now sleep only with synthetic sleep, and provide themselves with nothingness from the learned industry of organic chemistry! Perhaps new arrangements of more or less barbituric molecules will give us the meditation that existence increasingly forbids us from obtaining naturally. Pharmacology will someday offer us depth. But, in the meantime, fatigue and mental confusion are sometimes such that one naively finds oneself longing for Tahitis, paradises of simplicity and laziness, lives of slow and inexact form that we have never known. Primitives are unaware of the necessity of finely divided time.

There were no minutes or seconds for the ancients. Artists like Stevenson, like Gauguin, fled Europe and went to islands without clocks. Neither mail nor telephone harassed Plato. The train schedule did not rush Virgil. Descartes could lose himself in thought on the quays of Amsterdam. But our movements today are regulated by exact fractions of time. Even the twentieth of a second is beginning to be no longer negligible in certain domains of practice.

No doubt, the organism is admirable in its flexibility. It has so far resisted increasingly inhuman treatments, but, ultimately, will it always sustain this constraint.

- Le bilan de l'intelligence, Paul Valéry, 1935