Scrabox its completely and totally random in what it gives, unlike EMC where you can be precise and make whatever you need.
Recicler is also random in which you could get 64 scraps with 64 cobblestone or you could get nothing (Don't fall into the gamblers falacy people)
UU matter its a little like EE but only on the fact that you can choose what to make, you can't be precise on how many units you want to make nor you can make something with the bare minimum in most cases, its either all or nothing.