"SFF, Notebooks" forum is where you will find people who might know about this. It is hard to believe any externally connected graphics could outperform the internal graphics, even if it can be done.
But, you CAN have multiple video cards and drivers. It is not that unusual. Additional cards are all PCI. They used to have demos of this a lot when XP was introduced. I've tried it just for fun. Having onboard AGP graphics and an AGP card both function has been impossible.