Feel free to cut them off if they look ugly. On year one, bloomage tends to last too little due to transplant shock and the greenhouse conditions used for large plantings.
Hydrangeas in containers will need watering more often than those in the ground but it is difficult to say how often because so many variables enter into the equation. However, you cannot go wrong with something simple like inserting a finger into the soil to a depth of 3-4" and watering if the soil feels dry or almost dry.
I would suggest 1 gallon per watering but it may be necessary to water more in the summers or when the container gets large because the plant has grown. Or water less if the shrub size is still small. Try watering them a little, wait for the water to drain and then water again. I usually get plantings that fit around a 18" pot and switch to larger containers in 2" size increments.