Lifelong OC/MD goer here.
I used to stay in the higher numbers (high rises, etc) but found that I don't care for it anymore. The beach is very densely packed there because of the occupancy of the taller buildings but with the same strip of beach to hold those people. The benefit there, though, is that you get newer construction, amenities such as a pool, and maybe a bigger condo.
What I really have found that I like is staying "mid-town." This is usually between 45th street up through 80th street. This housing was built before they allowed high rises so the buildings aren't overly tall and therefore, the beach is not as crowded and you get that "old beach town" feel that I really enjoy. Most condos in that area have all been renovated so it's not like you're in some old flophouse. They will all have central AC but not all will have elevators so there's that. I have family that now own places around 52nd street and 62nd street and it's really my preference.
Boardwalk area is very bustling but there has been a lot of new construction in that area too, just not oceanfront.