If you're doing what GamerBoy357 said and applying a new layer of TIM on your GPU IHS, I'd suggest Thermal Grizzly Kryonaut (if you like conventional silicon non electrically conductive paste) or Coolabratory Liquid Pro (if you're into liquid metals, but electrically conductive). But unnecessary though as MSI doesn't do a bad application of TIM on their GPUs, naada. You'll probably gain like 3-8C lower temps and more if you use liquid metals.
RX 480's TDP is rated at 150W and so is GTX 1070's. Safe to say that an RX 480 would hotter than a GTX 1060.
Your case is an Enthoo M? What's that, an Enthoo Mini for mATX boards or something?