jmp1973:
Can't help you on specifics. I don't have any lights or lasers on my (was three, now two) M&P's. I have CT's on two small 1911's that I rotate when "outside", though. Just decided that I jumped when I shouldn't have. Great training aid, but, IMHO, not all that useful otherwise. One, you shouldn't depend on them, and two, the whole "operation" of the gun is different between a laser and the iron sights.
(I have a similar view of night sights, but since they're passive, and don't really change too much, it's a YMMV.)
IAC, for a laser, you want something that you can easily activate as needed, and shut off just as easily. Avoid "blink if you push once, steady if you push twice" gimmicks - if the stuff hits the fan, you'll muck that up. "Blink", too, might make it easier for the BG to find you.
Now about the lights.... I bought the M&P 'cause I wanted one

.... The rails, IMHO, are for a bayonet

.... LEO's can take the risk, and may really find having a light on their handgun useful as a "third hand", but I don't think the rest of us should take the risk of pointing a gun at
somebody just to light them up. Here in OH, do it outside of your own house, and you're in deep legal stuff, too, in some cases.
Again, though, if you prefer a light, avoid the "blink if you push twice" sort of magic. You'll muck it up anyway.
I'm a semi-retired rent-a-cop, among other things, and was trained to hold my flashlight in my weak hand, well away from my body, while my strong hand holds the firearm someplace convenient, and likely in front of me. Putting the light on the gun rail just seems to make it easier for the BG to make a mess out of me by aiming for the light. Not nearly as easy if it's in my weak hand, way out there.
(With a two hand technique that pairs the gun with the light, if you even think the BG is about to shoot, you can get that light the heck out of Dodge pretty quickly - much better, IMHO, than just shutting it off....)
Meantime, shoot the heck out of the new gun

.... Get used to it on the range, on your belt, etc. If you're going to try to get a license (i.e., haven't already done it), some range time before you get there - preferably with a half-decent instructor - will be helpful, and take some of the edge off the proceedings.
Regards,