Same problem with my iPhone 7 plus. It used to work normal after upgrading to ios 14, but after new version came (ios 14.0.1) problem with heating and battery drain started. While my phone is on standby, it could not stay turned on whole day (before update I didn’t had that kind of problem). And also i had problem with cyrilic letter Њ (if you are reading this from you iphone you will notice that letter is not right) the horizontal line that is continued on half circle of the letter isn’t straight, it has bump or something like that (i hope I explain it so you could understand).