I’ve actually found that my Strawberry Sundae Hydrangea has more flowers in a sunny spot. I do have to watch and give it extra water when the summer gets hot with no rain. Hydrangeas also do well in containers. But, in a container, I would probably go for a spot that gets morning sun with some shade in the afternoon. And, plan to water more frequently in the summer. Endless Summer has a great guide on growing hydrangeas in containers.
Thanks for writing!