If I want to have the 15" with the fastest processor and fastest video card will I have to order? Or can I walk into an Apple Store and get a model different from the base selections I see online?
They'll have the 'Good/Better/Best' configurations in store (when fully stocked eventually), and occasionally other very common configs, but you shouldn't count on anything but the base configs in-store.
If you want anything different, call in and ask what they've got, then decide how to proceed.
Configure to Order
Configure your MacBook Pro with these options, only at apple.com:
2.9GHz quad-core Intel Core i7, Turbo Boost up to 3.8GHz, with 8MB shared L3 cache
Radeon Pro 460 with 4GB of GDDR5 memory and automatic graphics switching
512GB, 1TB, or 2TB PCIe-based onboard SSD
They may have some configs in store like someone above mentioned, but call ahead and ask.
Thats what i'm going to do, was going to order online today... but the Dec 27th ship date sucks. Going to try my luck tomorrow with a phone call.