I've run M&M for over a decade as well. It's a fun game, but definitely a different experience than DnD. I prefer the 2nd edition of the game, because of some of the specific interactions of feats and options in the game, but 3nd has some nifty updates (that I've folded back into my 2nd edition builds). Afflictions is such an elegant design, I use the same concepts in everything.

My main advice is to play it fast and loose. There are characters that can teleport across the world, shrink to different planes or existence, and bench press the Eiffel tower. Just lean into it, and make sure the players are getting roughly equal time to shine.

Hero points are a great economy and it's okay to go meta with it. I like to bait players into it. "That building you're holding up isn't too heavy for you, but wouldn't it be a shame if there's a little old lady in apartment 3B still?" Once your players trust you're doing it to have fun and that screwing over characters is not the same as screwing over players, this can be a very rewarding way to play.

Toughness shifts are more powerful than accuracy shifts. As previously pointed out, it's not a bad idea to give Autofire to anyone accuracy shifted, otherwise the numbers don't quite pan out.

I use a "world made of cardboard" rule for characters. If their base damage for a strike exceeds the Toughness of a target by more than 5, then it's automatically lethal damage. This adds in a wrinkle for some characters that don't want to kill so they'll limit power against low level thugs, and then go hog wild with robots and big bads.

I also built all the characters in Excel. My players never wanted to do the actual builds. They gave concepts, I built them to points, they reviewed, I tweaked, and then we played.

I also allowed for trade-offs between offensive and defense to allow for glass cannon builds. For example, Cyclops could have a PL 13 attack with PL 7 defense in my game.

Finally, PL 10, in my opinion is too high to start a game. Because the civilian world is tuned so low, you can have very super super heroes at PL 8.