Tall three dimensional arrays

I am determine if the following is both doable and beneficial use of tall arrays:

1. Let's say I have a set of larger matrices A_1,...,A_99 , where dim(A)=800,000 x 600.
2. Due to memory constraints, (196 GB), I cannot hold the full A_k in memory.
3. I would like to take say, one entry ij, of each A_k , collect it in a vector v(1:99) for k=[1,99], then perform an operation on v - for each ij pair. Note I have 3 directions: the original of each matrix, and k as a result of collecting the matricies. And I am interested in performing an operation (fft) in the k direction, the 'tall' dimension of the tallArray.
4. Question (a): is this use of tallArrays somehow optimal, or at least not terrible?
5. Question (b): Save or not save each matrix to disk before calling tallArray? Since I have A_k in memory, would it be advisable to use arrayDatastore ? Or should I save each A_k into memory as a .mat file in the same directory, then create a datastore from the saved-to-disk *.mat files?