My advice if you're relatively new to the system? Stick to the RAW, and ignore all the alarmist ... everything ... on the forums.
A lot of the house rules listed are (as you mentioned) responses from over-reading the forums, but here's a few things I've picked up myself from running a few sagas:
A lot of the things that crop up as 'problem children' for early SGs are actually only problems if you assume that fresh-from-apprentice magi are not that far off what a mature magus is. When you step back and adjust your mindset to look at what a magus who has developed enough to not be a spring chicken is capable of, and the kinds of scores they have, you may adjust some of your views.
In my experience, magi mature into 'summer magi' at around 30 years past apprenticeship. This is not a short space of time, and many sagas don't even get that far and many more sagas make the mistake of assuming that someone with an art of 10 is potent in that art. A mature magus is going to have 20s in their primary arts, and 6-10 in everything else. This is still a relatively young magus! Older magi will either have a whole range of 15-20s or something at around 30-35. Take a look at some of the magi in MoH or at Phillipus Niger in GotF. These aren't 'munchkin' magi - they're just older.
So what does that mean for your saga?
Young fresh-from-apprentice magi are at the bottom of the pecking order. While they're going 'wow!' over a level 10 quality 15 summa, those older magi probably don't care. It's not going to get the trade value the players might think. And tractatus? Unless the magi themselves are writing tractatus, you can assume most of the tractatus in their library have already been read by most of the other magi around. And if these young magi make a song and dance about running a fantastic book trade from their amazing library, just slap them with a wizards-war raid or two by older magi until they learn to stop being so noisy.
Vis experimentation will be unpopular for young magi, because young magi treat teach pawn of vis as if it were a pound of gold. When they're older and sitting on a couple of hundred pawns they might not be so bothered about taking that effort to get hold of a tractatus they haven't read yet - not when that vis is just sitting there.
If your players do all create com +3, great teacher magi then they're obviously serious scholarly types. Sure, their books might be awesome - but quickly give them reputations to support it and the kind of attention (positive and negative) that comes with such. Again, wizard's war is your friend. Don't be afraid of it - it makes for fun stories. Just remember that most wizard's wars (like most fights) don't end with the death of one of the combatants.
All in all, my advice is don't try to hamper the growth and power of the magi unless it proves itself to detract from your enjoyment of the game. Let the system flex its muscles, don't react to the alarmist debates that litter these forums.
Ars Magica isn't the best game to tell stories about struggling against adversity with no assets. It's better for stories where the players have and have access to an incredible range of assets - and it is only with those assets they can triumph.
That said: core rulebook only for starters is a good move. Let other things drift in as needed, or you'll find yourself overwhemed.