A "beginning" Sorcerer can be useless... it depends on what you are using for a Previous Experience system. RQ III used age (2d6+15: avg. 21 years) to determine the number of points that a player had to allot: 30 points per year if you were using the buy system, or a certain number of points in specific skills if you were following a template. So using the average, yes a starting Sorcerer (age 21) would be somewhat less powerful than a 40 or 50 year old veteran Sorcerer who spent all his time focusing on his magical studies.
In the BGB, this is not something that needs to be worried about. It all depends on the Power Level of the campaign, Edu (if being used) and cultural background. A competent Sorcerer should be able to be developed at the mid to high Power Levels.
They are not represented in the BGB, but other systems that I would look at are the ones in the Elric/Stormbringer supplement The Unknown East, and the "Western" system presented in the Nephelim supplement Liber Ka. The first is somewhat freeform, the second formed around elemental "schools" or "arts".
As far as categorization of what is in the BGB, I'd have to agree with those above. They can really be categorized however you will. Determine which system you prefer based on the flavor of your campaign.
SDLeary
SDLeary