First of all. Virtual riot started studying music production at a pop academy where he lives and he learns how to use stuff etc as he explains in this video.
Zomboy however used to be a sound engineer so he knows a lot about sound design and music production hence how he has such amazing and in my opinion the best mixdowns for his track and he uses stuff like FM8 and Massive to achieve his sounds and if you look throughout this thread you can find myself and other users posting on how to achieve them sounds I'm sure you'll find it all helpful! Here's a patch I made to help you guys copy and learn from it.
I'm not too sure about must die but I'm sure he just learnt about music production and trial and error or something But Must Die's sounds are very similar to the zomboy sounds and I'm sure you could experiment and see what stuff you can make Here's a patch that Omegamode used in the mutated second drop and if you get the arrangement right I'm sure you could beef it up with post-processing make something awesome