After reviewing tape, and in one case spending 20 minutes rewatching one play until I got it sorted, I can make a few conclusions. Geno Smith executed some plays really well. Milliner got really lucky on his pick, and Coples was half of the reason for an early TD.
Let's go defense first and look at the first TD of the game for the Browns. Here's an example of Coples getting caught outside and the power working perfectly against the Jets 3-4. Also of note, I'll point out why 3-4 ends need to force double teams.
Here we go. The Browns got the ball on the Jets 5 after a long drive. The Browns go with a heavy package. This is an example of a power or pull power as some coaches refer to it. The guard and TE both on the right side pull and become extra blockers for the play to go left. The FB does a decoy route and doesn't even block. The RB gets the ball as shown. Line blocks as shown below.
Coples here is the key block. He's the bottom-most guy down on his hands. He runs straight upfield and gets caught by the pulling guard. On the inside 94 Harrison gets doubled which isn't unusual.. The problem is he doesn't keep both lineman on him by pressuring. He allows one guy to slide off and gets the LB as shown. That took care of Davis as the lineman got him in the hole. Harrison compounds his mistake by overplaying and getting shielded to the inside. Here's a look at what happens with the combination of Coples and Harrison getting shielded. Side note: everyone else does nothing to get off blocks or read the play. The guys at the bottom including Cromartie are on their man so I don't fault them too much.
What ended up happening is a giant hole in between them. Here's the view at almost the same time from behind the play which has a better look at the hole.
That, my friends, is two guys overrunning the play. There's nobody other than the LB left who gets picked up before the TD. Needless to say that happens. Again, the side view here is showing the two guys getting caught and everyone else being blocked.
This is the back view showing a lane straight into the end zone from maybe a half second or two later after the side view. This is an easy TD for the RB as Harrison eats Metlife Turf and Coples tracks his man from the 12 yard line.