Square leading edge means the splitter won't have a "knife-edge" anymore. Instead it would be squared off, which makes me think it will have to work more to cut through the air, therefore helping slow the car down plus give them the downforce they're looking for.
As far as limiting RPMs, I agree with what a lot of people were saying about 2013. They were going way too fast, NASCAR has never been known to do speeds in excess of 200 on a regular basis. Slowing the cars down will let them have more control of the car, and be able to maneuver a lot more. Hopefully resulting in more side-by-side racing and passing.
And more pileups... Seriously, the "crash factor" was non-existent for me this year. It took a lot of fun out of the plate races. Among other places where we usually see some decent wrecks.