My Son has a early production S&W M&P full size 45.
He would like to refine the trigger and sights.
He enjoys shooting my pistols, most all have fiber optic sights.

I was investigating changes to his gun and feel the Dawson competition fiber optics would be something he would be happy with.
As far as the trigger, I come up with the Apex competition trigger enhancement kit and a replacement trigger. I'm not sure what the advantage is in replacing the trigger with the Apex trigger or will the stock trigger work as well with the Apex Comp. trigger kit.
Apex suggested to NOT use the spring that comes with the Apex competition trigger kit but to use the spring that comes with there replacement trigger.

If anyone has done these mods on a original M&P 45 I would like to hear your advice.

Any other modifications that might be worthwhile?

I've reworked several M&Ps. I Highly recommend that you read over the following:

http://www.burwellguns.com/misc/M&Ptriggerjob.pdf

Excellent overview on how to rework the factory trigger. It's easier to drop in new parts but this article gives you an idea of what and where improvements can be made.

https://www.apextactical.com/d...ment-kit-for-the-m-p

Bang for the buck I think the above is the best overall improvement that you can make. I found the rounded dome on the trigger safety made the biggest improvement on MY triggers.

If you hate the factory trigger geometry you can always add a flat trigger or whatever later. But if you have skills you can vastly improve the factory trigger without spending money for new parts. You can add some more precisely made Apex parts at a reasonable price. Or you can buy a full blown Apex trigger system that makes a huge difference with drop in parts.

Honestly evaluate your skills and willingness to spend and there are lots of different ways to get nice triggers in a M&P........

Thanks for your advice.

I have an original M&P 45 as well, I installed an Apex kit: sear & sear spring, safety plunger and spring, but kept the stock trigger spring in place. The pull is right at 4 lbs, but has the stock vague trigger reset.

I also, have a M&P .45 1.0. I went full Apex with the aluminum trigger. Super sweet. Probably the one gun that I would never sell. And Night Fision sights.