I too am having the same problem, I am running the most recent IOS 14.0 update on my XS Max and have noticed a significant loss of battery life throughout the day. Also I have noticed my phone tends to radiate an excessive amount of heat when doing things on my phone that would usually not cause any amount of heat to come from my device - such as scrolling through social media or reading a book. I had an overheat warning from my device yesterday whilst reading a book, which made my device unusable until it had cooled down. Baring in mind I was sat indoors out of direct sunlight in a room that was maybe touching 18 Celsius. Just writing this comment my phone has started to produce heat and reduce the brightness.