I think I can answer a part of your question - we did a lot of "mathing" and calculating, how many meters with how much weight a block would have and how many pixels one meter of material would represent, then played with the numbers until it felt right. We really wanted to drive home the feeling of heavy concrete blocks and a (reeeeaaally) powerful cannon, so looked at reference photos and videos of collapsing buildings and stuff ^^ It was A LOT of playing around until they didn't feel like paper boxes anymore haha