I built this machine mainly for gaming (VR as well) with portability in mind. I'd never built a computer before and have a lot of thanks to the SFF community for all the recommendations. Also, massive props to the creator of the S4 Mini, Josh Sniffen. The guy is an amazing engineer/designer/creative/person and has incredible videos on a lot of things SFF.
After completing, I'm extremely happy with the build! Stock, the 1080 mini had a slight coil whine (which may be more noticeable with the S4 Mini) but I was able to to undervolt the GPU following this youtube video and the whine is now practically inaudible!
I wasn't expecting the 330w power brick to be so massive.. definitely makes me consider doing a brickless build but I prefer the extra power of the 1080 vs. a 1050ti.
Stock has a slight coil whine but appears to be remediable by undervolting.