I have a maga that i love, ( i wrote nearly 25 pages of history for the SG)
The fact is that i do know that Arm5 is not a munchking-proof sistem but a storytelling.
I want not to abuse the sistem but to improve the experience.
My char have two virtues that in some point, somehow, stack or lookslike. Both are major.
Faerie raised magic HoH:MC 86
Comprehend magic HoH:S 128
Through the first it can invent spells that copy efects of supernatural virtues on the fly of an adventure, no lab no study...
With the second get insight of the magic from a creature or magic. and multiplies magic theory when investigating an spell and up to SG give bonus in integrating that hermetically.
So if my char studies a gruanach and copy its spells and pas them to a bonisagus?
As it copy the spell also mimic a posible new BaseDuraionRangeTarget.
So, if for that spell only the new limit is stable ...
if i write it down the spell or teach to the boni. countss this as breaktrough points for the breaktrough?
on a normal adventure i can copy a fifth magnitude spell on a good one a seventh.
what are your PoVs?
Faerie raised magic lets you invent spells on the fly for a large xp cost, instead of a season of work , which is not bad for a major virtue. It does not let you break the rules of Hermetic magic. So you cannot learn a spell which does not use the standard effects, targets and ranges unless you have them through another virtue or breakthrough. Nothing about this helps make hermetic breakthroughs or helps gain insights.
Comprehend magic allows you to gain more understanding of none hermetic effects, this understanding does not give you access to the none hermetic magical features of say a Grugrach . Specifically wether or not it helps with breaktrough research is GM decision. Nothing about it would mean that I would allow you to copy a none hermetic effect.
The two do not really combine . It certainly does not allow you to routinely share these insights with another magus,
So your specific question
Can I study a Grugach and pass the spells to another magus. No. You could only invent a spell based of a Grugarchs magic which hermetic magic could already duplicate. Perhaps if you and the other mage spend time studying Grugarchs this may help with Original reseach or Integration allowing some approrpiate experiments or maybe if your GM is generous an autoamtic insight
I see nothing about the combination which allows you to copy none hermetic effects and so it is not a clever rules abuse as the two Virtues do not help each other
Formulaic spells are not bound to the standard R/T/D. Spontaneous spells are.
With Faerie Based Magic you can invent Hermetic spells outside the lab to duplicate Faerie powers, supernatural spells or Hermetic spells observed by spending xp . These must still conform to Hermetic guidelines. There's no Breakthrough there. If you observe a Learned Magician casting one of his Virtue-granting spells, or a Gruagachan doing the same, there will be no duplication.
I would not be opposed to house ruling this helping you gain Insight in some way to attempt later on to invent , in the lab, with Experimentation, spells/effects to maybe integrate this into Hermetic Magic.
Comprehend Magic is another separate matter. Again, I would not be opposed to this character analyzing some hedge magician and his powers, under some controlled manner (the Lab) and gaining Insight (and a bonus) to start the long road to Integration. This is actually part of the wording of the ability: At the option of the storyguide, this Ability might also give an insight into adapting non-Hermetic magic into Magic Theory.
This is correct, though using non-standard R/T/D in spells is generally of higher magnitude than it would be if those same R/T/Ds were properly integrated into hermetic theory. So if you saw a Holy Magus use the "Presence" range (equal to Voice IIRC), you'd have to invent your spell with a Range of "Presence" that was equal to Sight.