I’m my experience the stock plastic parts work fine for most of the car, & aluminum upgrades upgrades are way over hyped. The only thing aluminum parts really do is add a bit of color & extra durability. That said, as you can tell from my build, I love adding color and personalizing the chassis to make it my own.
The aluminum parts I consider to be useful will be listed below & order in terms of their importance:
#1 Differentials
#2 Aluminum motor mounts & heat sink clip
#3 Adjustable front suspension arms (threaded)
#4 (DWS) MPower shock tower & Arm holder
#4 (stock rear end) Teflon rear camber knuckles
Everything else is really for show, or for durability.