Another question: What would be the optimum number of medium frames, with brood and bees, to do a walk away split.
what kind of split do you want to do? If you have one hive and are splitting it a walk away split is pretty much taking 1 or the 2 brood boxes and placing it on another stand. The box without the queen will make their own.
In a normal split you're moving about 1/3 the frames and bees into another hive body. Another way is to rob 1 or 2 frames from each of several hives and creating a combined split. This leaves the original hives much stronger while still increasing your hive numbers.