So far, after buying 11 different (and returning them) 3 in 1 chargers from Amazon, this is the ONLY one I found that will reliably charge the iPhone 12 Pro Max in a Mous case, and will charge my Airpods, AND will charge my Apple Watch series 6 reliably (it use you actual Apple watch factory charger snapped into the case).
https://smile.amazon.com/dp/B08GFY7TDK/ref=cm_sw_em_r_mt_dp_I7M-FbT2AGQWH?_encoding=UTF8&psc=1
It is a cheap feeling charger, and not the most pleasent to look at. That said, it just works, and it's the ONLY one I have found that will work with all 3 of my devices. I have found some that would work with the iPhone 12 Pro Max, but then not charge the watch. I have found some that charge my watch, but not my iPhone, and found one that did great on those, but wouldn't charge the AirPods (but would work with Airpod Pro's). If someone has a nicer one they find that work with all three, PLEASE let us know. I wish we had a new thread to list the known working chargers.