With 4 wooden boats at each davit, they probably would've been stacked on top of each other, I don't think there was enough deck room to store them inboard of each other.
If they had to abandon ship with multiple boats at each davit, they would lower a boat to A-deck, load it through the 1st class promenade, lower it to the water, then bring the falls back up to pickup the next boat amd do the same thing again. The enclosed forward portion of Titanic's A-deck promenade would make it a more difficult, as seen with the launching of boat 4 in the actual sinking. The Olympic's was open the whole way around.
On the sinking of Britannic in real time, I think they show the gantry davits going over inboard to pick up the next boat. One of them is shown in a stuck position, noted in the simulation.
I'm not sure these could be launched very quickly in the event, unless you had plenty of time, but ships don't often give you that.