I'm wondering if there is a way to make on object go through only one other object. So like if there were 2 cubes, the cubes would collide, but they would not fall through the baseplate.
Take a look into collision groups, this should allow you to achieve what youre wanting. https://developer.roblox.com/en-us/articles/Collision-Filtering
I'm not really sure what you mean. If you have CanCollide turned on for the bricks then they should collide anyway.