I don't have the m3 model.
I think the m3 will heat up, but I don't expect it to heat up over 80 degrees due to TDP. The i5 model gets to 90+ temps when I game on it.
I Reset both of my m3s a couple or more times, ran benchmarks on them, and never noticed them being hot. I didnt run any games or extreme stress tests though. At 4.5W TDP I don't think it's going to get that hot.