Storage block GUI confusion.

I'm trying to make a humongous storage system, similar to a shulker box and my small brain is struggling with the GUI. So first of all, if I have Drop items from inventory when destroyed disabled, will it act like a shulker? Second, I'm having issues with slots and gui. I tried making one as a container, but that couldn't be accessed and I'm working on a gui now, but I don't know how to add slots. I also don't know if I should be using procedures, or input slots or both. Ideally I'd like a copious amount of slots, like 128. If this is possible I have no clue how. 

Thanks.