I was looking at the Calculated kinetics dog tag and the C&H. With the dogtag does the optic still screw directly into the slide? Does it really help keep the lens from getting smoked?

The DPP 407k plates are really good.
They are low enough that you can use the factory sights from an M&P metal.

I ended up getting the Calculated Kinetics plate and it works great. Did you have any issues with the lens getting smoked?

Didn't care for that particular plate as I wanted to use low height irons (.250 front / .365 rear) from Dawson which I think looks way better on the gun that the tall factory ones.
I have shot thousands of rounds through numerous red dot optics and have never had a smoking problem with any, so respectfully, to me its a solution looking for a problem.

What's wrong with the oem plates?

They're polymer.  I'd rather have metal recoil lugs.  I've actually gone to the Holosun SCS so I can direct mount to the optics ready footprint.  I'd rather have my slides direct millled for a specific optic than the plate system.

ANY MOUNTING PLATES I SHOULD AVOID?

Have there been failures, or just personal preference?

Those "lugs" aren't for recoil but are simply locating posts.  The resistance to recoil comes from the clamping force of the mounting screws which thread directly into the slide.  Ensuring proper installation (clean threads, correct hardware, proper torque and thread lock) will provide trouble-free results.  Witness mark the screw heads because if the screws show any sign of loosening, you have to redo the installation or be prepared to have your red dot fly off the slide and hit you in the forehead.

All of the failures I've read and heard about are due to screws loosening (under torqued) or breaking (over torqued).

And the nicest plate I've seen for the OP is https://eleven71design.com/shop/p/mp-20-holosun-eps.  Probably way too pricey.

CK Dog Tag plates are great!  Fit is great and the the tall lip actually works great in my opinion...