Hi. I've been playing with my M5Stack a few days. I would like to give some feedback to you. Overall, its great. Love it!. But it is not perfect...though very close. Well done. A few things I'd like.
PMU be more integrated with the ESP32. The ESP32 has a hibernation of just 5 µA so could be physically powered on all the time....but in deep-sleep mode. This works anyhow, though I am unsure how much current draw the other components inside might use when in hibernate?
The biggest annoyance I have though is with the M5Stack software. It is not built particually modular. For example, I wanted to get faster screen graphics and there is an optomised driver available here: https://github.com/Bodmer/TFT_eSPI - I managed to get this working on the M5Stack. However, I had to remove completely the M5Stack.h Which meant I was on my own getting the other things to work, creating everything from scratch.
If you can play well with other software out there, for the ESP8266 and arduinos, it would be so much nicer!
But, overall this is a wonderful piece of kit, and I offer suggestions only to make it even better.