Every floor at BCV is accessible. There are two elevators near the main entrance and a third by the pool door.
We haven't stayed at SSR but I believe people have posted that there is an elevator in every building there too. I'm sure someone will be along to help you about SSR.
At SSR, BCV, BWV and VWL, all rooms are accessible by elevator and therefore ECV accessible.
However, at OKW not all buildings have elevators. All units on the first floor or each building are ECV accessible since their entrances are at ground level. However, units on upper floors are only ECV accessible in those few buildings that have an elevator.