Who drove numbers and technology in the dreadnought race

Was Germany's biggest contribution to the dreadnought arms race the number of ships built rather than technological leadership?

Largely yes; Germany drove British numbers, while Italy, the United States, and Japan also pushed technical development.

The compact answer separates two kinds of pressure within the dreadnought race. Germany's programme primarily forced Britain to maintain a larger numerical lead. Italian, American, and Japanese construction helped push technical development and larger designs. The naval race was therefore not a single bilateral contest in which Germany caused every innovation. Watching this exchange helps distinguish force-quantity competition from the wider international competition over ship capability.