We use the packets instead of the cups because 1) It's cheaper and 2) I don't have room in my cabinets for the 100 servings my kids eat in a week.
1. Deal with the overflow
I love these bowls/plates from Ikea. They are inexpensive and the bowls are perfect size for Easy Mac. I put the bowl on top of the rimmed plate in the microwave and it catches the eventual volcano.
2. Too hot to handle
No kid has the patience to deal with waiting till the mac cools down. And I have way better things to do than sit and blow on it. I have previously put it in the freezer, done the cooling plate, but found a better solution. When it comes out of the microwave, usually most of the water is gone (if not, put slightly less water to start). Drop in two ice cubes and stir till diluted. It cools it down quickly and gives it extra moisture so the cheese stirs in better.
3. Deal with the mess
After rinsing off the spillage from the plate, I put it back under the bowl to catch some of my kids fork to mouth misses. Everything that hits the ground belongs to the beagle.