All the accumulated evidence for beach landings up to June 44 showed the necessity for ship based support fire. Air support wasn't accurate enough nor as responsive. Air was best used to cut communications with the landing areas and take out one or two large, fixed targets and to provide air cover to protect the landings.
AFAIK the terrain behind the beaches in Normandy was not factored in at all - the importance was a large area of good beaches so that they could get a large force ashore within 24 hours and not get hung up by a single point of failure (such as the problems at Omaha). They should have prioritised a rapid push inland within 24 hours but once ashore they dug in (as at Salerno). Although fighting in the bocage was tough I don't think it was as bad as the terrain in Italy where the Allies struggled for nearly two years making very very slow progress