McVay may use a lot of 11 personnel alignments, a lot of motion and misdirection with different options off of each formation/play set. The personnel at WR is also key as the XYZ positions can all run all the different routes making it even more confusing. Plus the WR group are all good blockers further enhancing the advantages of the 11 personnel grouping.
The net effect is that McVay spreads the field vertically and horizontally so that the defense needs to cover the entire field. When you force the defense to cover the entire field it usually leads to more DB's on the field and a more spread out alignment of smaller defenders. Tackling Gurley with a head of steam is not easy but it is much harder for smaller players. Once of the reason that the screen plays work so well is that the defenders are spread out and we have big people blocking smaller people. Size does matter regardless of what people say.
McVay is the genius to figure all of this out and take advantage of the great talent that he is given to coach. There are coaches that have great schemes and fail to produce premium results because they fail utilize the available talent to maximum efficiency. The Rams do a good job on both sides of the ball put players in position to be successful.
5-0 you gotta love it.