Another iPhone 15 user here with the same heating and battery drain issue since updating to IOS 17.5 and then IOS 17.5.1
I was hoping 17.5.1. would fix the battery drain and heating issue but it hasn't... Battery brain is 20% to 25% overnight... It was usually no more than 5%... I've had about 3 models of iPhone at this stage (iPhone XR, 13 and currently 15) and I have updated each phone multiple times and this is the first time I've updated and experienced as bad an issue as this... Ironically enough one of the reasons I switched from Android to the iPhone a few years back...
I decided to erase the phone and set it up again from an iCloud backup... A little bit of a pain to do but if it resolves the issues it will be worth it... I will update this post if it improves the battery and heating situation but it will be a couple of days before any difference will be noticeable...
It's disappointing that Apple would release an update as bad as 17.5 and 17.5.1... I'll be waiting for the online feedback on any future IOS updates before upgrading again... Experiences like this diminish trust in Apple's competence...