Delta Airlines: Hand luggage

Did anybody already fly with DELTA Airlines?
Are they very strict with hand luggage? Is it possible to pay an overcharge?

I need to take my laptop and a camera (fits easily in the upper locker) + of course a bag on a transatlantic flight - according to their infos on the website they only allow 1 piece of luggage.

Why can't the airlines not adapt their weight and luggage regulations to each other - with South African it is no problem, but then I change the plane, and suddenly I have too much luggage???

Thanks for your experience!