Does this rating matter, do bump & run influence the outcome of pass plays (how, slowing the route progression?) I never saw a corner "press his receiver on the line" and they invariably start several yards from him but maybe I don't interpret correctly what I see. Thanks in advance for your input!

There is a decision that your CBs make to decide whether to play off the WR or play close and bump and run. Usually this decreases with faster WR's so the CB doesn't get beat; you'll know if the CB is playing bump and run because he'll be right on the LOS when the play starts.

B&R will slow the pattern down (depending on the WR's B&R avoidance) because the WR's velocity is interrupted. This potentially could give the DL a bit of extra time before the WR completes his route. So it doesn't have a huge impact, but may tilt the scales slightly on some plays.

Is the impact enough to make it seem like speed DEs are better than they are on some plays? Just wondering if this could be contributing to the "DEs are overpowered" argument.

It's possible, but I don't know that it happens frequently enough to have that noticeable of an impact.

I am thinking specifically about in the Singleback 4 Wide formation, especially when the HB(s) is not good at pass blocking, or in empty backfield sets.

Under the current code fast DEs just run down the QB as he goes toward the sideline. Soon to be implemented is the pass blocking interactions will include the mobility of a player determining different outcomes that are currently regulated by pass block vs. Pass rush numbers while the two player are engaged. It is to simulate true speed rushers. Or at least that my take. Cause now a fast DE with little else will sack a QB who won't run.

I am thinking this newer code will make B&R matter more as the QB seems to be making more decisions back there in MFN 1 beta test league. If a Blitz is coming heavy and CB blow his press or coverage with out any recovery speed it is almost a guaranteed TD against a legit QB WR combo.