The major difference from a VPP is that you gain the basic "pool" for free, and increasing it is cheaper than it would normally be. The major difference between this and the standard Resource Pool is that it doesn't deal with things that can be stolen or lost on an individual basis -- someone who steals your grimoire (or one of your grimoires) gets all the spells contained therein.
The level of your Spellcaster perk defines the maximum Active Points of any spell that you can learn, with the basic level (40 or less) corresponding to the Weaker Spell versions of most basic spells in the HSG.
Yes, the Real Cost (not the Real Cost divided by 3) determines if you can memorize it, allowing a basic caster to memorize two or three spells at most. I don't really like the "divide by 3" concept, as it seems to come out of nowhere, and doesn't reduce the cost of spells nearly enough in the current edition, as witnessed by the fact that Drudaryon's Legion's spellcaster has to have Experience Points when none of his colleagues do.
Thank you for the welcome, although it appears that I've been here before and forgotten my own history ...