Some of this is a bit of rehash from the previous campaigns I've run - magic users are not particularly well liked because they are all dangerous. Some of it is new and will help define the custom playbooks I eventually put together. This is more to set a tone and establish some language.
These folks are born into the arcane through blood. Not necessarily the blood of their family, but some other strange source that gives them a direct connection. They develop their personal gifts through whatever strange ritual and method they can work out for themselves. While they may have brothers, they are all alone in the world. Many don't make it past their first spell as they try something more than their fragile mortal minds can handle and the raw power of the Patchwork rips their sanity to shreds or a Thing from the Otherworld steps through and does something unspeakable to their flesh and bone.
More limited in scope, wizards learn their powers through the study of ancient tomes filled with esoteric knowledge. They don't have the raw ability of the Mage, but don't mistake them for weak. With the right incantations the Wizard can tear a hole in reality and turn his enemies bones to steam. What the wizard lacks in flexibility they make up for in stability. Of course they all go mad eventually as the Patchwork worms its way into their brains - it is a fate that all wizards know is their destiny.
Where mages tap into their natural conduit to the Patchwork Kingdom and wizards learn and devise new spells, Sorcerers engage in the darkest of rituals to summon things from the Patchwork, from the Void Between Space, or who knows what else. They were likely mad before they went down this path and whatever darkness is tainting their soul only invites them to travel faster. The sorcerer is the bane to what little society exists - they wish only to enslave, destroy, hoard ancient secrets, or continue their "Great Work".
How Scions Fits In
Mages find things of Scions to be absurd and have little interest in them. Wizards understand that Scions has created artifacts with a kind of magic they are working to understand as well. Many sorcerers embrace the Gifts Scions - in fact some are almost entirely devoted to this path and have only a drop of arcane ability.
What About Society?
Mages and Wizards are tolerated in Haven as long as they don't throw around any spells. Outside of Haven who can say - would an isolated village understand the difference between a mage and sorcerer? They both have a darkness in their eyes. A wizard and sorcerer may look the same if they are kitted out with strange devices. No sane man will interact with a sorcerer if at all possible, but if they will work with one of the PC arcanists is best determined through play ... chances are it will go badly though. Anyone who can accidentally summon a demon is usually not particularly welcome.