I wrote this up explaining to a Texans fan how exploit match ups in our offense, and comparing it to what O'Brien has attempted to do in Houston. It applies to our game plan vs. Denver:
The way that you use the EP flexibility is to manipulate match-ups. Suppose you think a team's LBs are bad in pass-coverage. You go to 21 personnel (RB, FB, TE) to get their team into their base defense (only 4 DBs). Then you spread the field with 4 or 5 wide, often putting the FB lined farthest wide. The other team either puts a LB in the normal outside CB spot, or wastes a CB on your FB. If they choose the former, the entire defense is playing in roles they are not used to. If they chose the latter, you now have your receivers lined up against their LBs. Furthermore, you can figure out if they are in zone even before you put a guy in pre-snap motion. You can rip teams apart in the passing game like this, and you keep going no huddle so they can't get out of base.
Eventually, they might realize they cannot defend the pass in base against 21 personnel. They swap out a LB for a DB, and you pound them in the running game. This is how scrub running backs put up 200 yards against Colts.
To be able to achieve any of that described above, you need smart RBs, WRs, TEs, etc. Every player needs to understand every part of every route concept. The FB needs to know the inside, middle, and outside of the three man. This is why the Patriots value versatility and game-intelligence in their players. Perhaps OB wants to be flexible like this, but he does not have personnel that can do it. @steelbtexan has been arguing similar things. The Patriots have moved on from talented players because they could not pick up the concepts.
*(I am talking about EP as the Pats (and sometimes OB) do it. The article linked goes into Pats style EP more. I am not convinced that all teams that use EP actually employ these themes enough. The Steelers' take on EP always seemed a bit more bland to me.)