I have two Gen 1 M&P 9mm.  One is a PRO CORE and the other is stock.  The PRO CORE model I have is from when there was no trigger upgrade offered on the Pro model.

I have two very different triggers on these

Pro CORE
Breaks early in the pull, you with the wall with about 1/4” of pull
6 lb trigger and the reset is fast(spring pulling it back is strong) but silent

Standard m&p
Trigger press breaks at the back of the pull, all the way back, think staple gun
Reset is loud and faster

Is there known different triggers in the GEN 1 series?

Your PRO CORE model probably has an H trigger bar but not the updated slide stop with the bump, which actually makes the reset fairly nice.
I've owned 4 Pro and Core models, all had the H trigger bar but not the updated SS.

Your std M&P might have all the updated parts.

With all updated parts my current core was just as decent as the 2.0 triggers. The only thing that sucked about either one is the stupid hinged trigger.