I think the Shanahan (Sr.) system with Elway was smaller, more mobile lineman. I think we ran this most of the time McVay's been here - maybe we change scheme next year and go bigger. You have to ask den of jim youngblood about this. I'm pretty ignorant about outside zone scheme, etc.
For defense - the reason running game have come back is that people like McVay figured out how to stress big physical defense out - by spreading them out and making them defend the whole field. So guess what? Defensive coaches responded by running smaller, faster players who can run sideline to sideline. Most teams are in nickel a lot throughout the game. Unsurprisingly, power running can exploit this defense of cheetahs by knocking them over and over til they're done.
this is all an over-simplified analysis based on my very limited knowledge of x's and o's but it's what I've been seeing and reading about.
