As the OP, I'm more than happy to stray down this path.
How society treats gifted individual and how they react to that treatment is key.
I basically see the options as:-
The continual distrust and downright hostile behaviour gifted people endure, hardens their heart. Gifted people look for villainy and bad dealings in every interaction, including with magi.
Gifted people have been treated so badly, when they have a group that don't hate them, magi with Parma, as they've been starved of decent social interaction, they are happy to interact, happy to colaborate and spend time together.
Realistically there is no one way people will react. Suddenly faced with a strong irrational distaste for someone some will rationalize that feeling, will trust their instincts and believe their intuition is telling them something important. Others will suppress the feeling as irrational and might try to examine it later to see if it indicates some sort of flaw in themselves. Redcaps are able to suppress their reactions with a bit of training (not enough to warrant a virtue or ability) which relies upon being very familiar with the effects of the Gift and recognizing them for what they are.
While the Gift reaction is the root cause for a lot of Magi reactions, I wouldn't call them "petulant man-babies".
The closest analogy I am imagining is that Magi are not Subjects/citizens of a polity called the Order of Hermes, instead they are a community of heavily armed Sovereign Citizens bound only by the social contract called the Oath of Hermes. Many of these Sovereign Citizens are in competition with other sovereign citizens for limited resources (Vis, apprentices, Magic Auras, etc)
Even the Oath of Hermes can seem like an onerous restriction to sovereign citizens, so negotiators between magi at Tribunal have resulted in near freedom from the Oath for Magi in their sanctums.
If you were a King, how comfortable would you be in allowing a heavily armed foreign potentate unfettered access to you castle that is the center of your rule, containing your treasury, archives and other private details?
I am the first to admit it is a limited analogy.
And then there is that two minute period (at least) every dusk and dawn where you have irrational paranoia regarding your guest...
The whole HRE vs popes, Borgias, half the English kings... MA was filled by "petulants" who believed and demonstrated that Might makes Right. Imposing our modern culture is misguided.
Impotent words are not magic, the lawless Wild West is gone. You'd have to pick African warlords as nobles, and corporate interests as magi, if you want a closer analogy. How likely would Monsanto invite Shell to their sanctum?
I'd hope magi are smart enough not to be near each other at that time.
Even I'm not naive enough in my "Really, can't they behave like adults" vibe, to think that the magi would be dumb enough to see each other without the Parma.
I'm pretty sure just like in the modern era, there are some people with "Don't talk to me before my morning coffee", there's "Don't talk to me before my morning Parma".
I'd think magi in the same covenant, if they have cause to travel together, have separate tents or whatever, so they don't see each other before the morning Parma.
I may be biased in thinking that certain Lab procedures may be aligned with Hermetic durations, causing the occasional Lab activity to go beyond the Sun boundary.
eg stir the alembric until Sunset, then immediately use to paint the magic circle.
Though I don't know if there is anything canon about that.
It exists, but it's not the default. Per covenants, the standard hours of work for a magi in the laboratory is 10 hours a day, 7 days a week, and not all magi work the same standard hours - it will vary from magi to magi. So for the average magi not living too far north, the standard lab hours can fully fit from either sunrise to sunset or from sunset to sunrise for the nocturnal ones, most of the year. Most magi aren't subject to specific activities in specific timeslots, and even if they can't fit their lab activities, could interrupt their lab activities for 2m to perform the parma magica ritual if they know when to perform it.
And then there are the magi who have the planetary magic mystery. Those ones, yeah. They check which time of the day is astrologically favorable for things like stirring their alembic just right, and they may have specific actions to perform in their lab that happens to coincide with when their Parma goes down. But only when their perform an horoscope for their lab activities.
Let's not forget that every magus is probably capable of recognizing the effects of the Gift by what it is, and that during apprenticeship every magus had one 2-minute period in the morning and one at night when his master had to redo the Parma. And a few of these would likely be 4-minute periods (if the Parma goes down when they are together, I'd assume the master raises his Parma first, and only then protects the apprentice).
If a magus manages to go through that during apprenticeship I find it unlikely for 2 occasional minutes of mutual daily paranoia to be a problem for cooperation.
And of course, as always, I'm assuming the magus is cooperating with another rational magus. One he is on friendly terms with, or one who is paying (or being paid) for a service you both agreed beforehand.
I expect that would be the norm, but I also expect there would be a lot of deviation from that norm. For example a master could have staid in his private chamber until they were done with their own arma and quickly extended it when they saw their apprentice. On the other extreme a less organized master might well have neglected to do their own parma until noon on some days.