Hey mjbok - yeah, no worries - any time.
I too was thinking about using the foam blocks that the batteries came in, but after laying it out, I thought it took up too much real-estate for my needs.
As for the props, I store them under the drone (see pics) in the middle slot. I also keep my fiber cloth tucked away down there - the fiber cloth also protects the blades a little.
I store all of my wires in the bottom right slot - that slot goes through two layers of foam, so plenty of space for them there.
You're correct - I use my everyday iPhone X. But, like you, I'm thinking about buying a dedicated device. I left the spot to the far right, where the two memory card cases are stored, for either a phone or small tablet - there's plenty of space for one there.
There's also plenty of storage space behind the top (lid) piece of foam. I store my AMA and FAA cards, along with instructions and additional memory cards (see pic). I just stuck a shipping label holder onto the plastic. It works well, but I need to get a bigger one that will allow for stuff to go in there. In looking at the upper piece of foam, I was also thinking about cutting slots in the sides (or top/bottom sides) of the upper foam to store additional blades, memory cards, etc.
I hope this helps.