Westside lifters squat very wide because they compete multi-ply.
I don't see why a lifter would set up speed squats differently from regular squats, but then again, I don't really speed squat. Maybe I'm missing something here.
I wouldn't mess with briefs unless your hips were giving you trouble, or you were interested in playing around with a little gear.
Slightly off topic (and this isn't meant to bash you, OP): It seems like a lot of lifters assume that they should be doing what they're seeing in videos of "the big guys" because they're obviously doing something right. But, they forget that they are not at the same level, nor are they in the same gear.
The guys you see in WS videos and on EliteFTS are on top because they have figured out what works best for them as multi-ply lifters, and while there are many things to be learned from them, what they are doing isn't necessarily what is best for a raw or single-ply lifter. A few extra layers of canvas can make quite a difference.