Heat issues .. poor optimization?

I'm having heat issue. phone heats up to around 100 during normal usage (texting, web browsing, social media) and unsuprisingly gets much hotter during games or youtube, around 105 F. Those temps are from a batter app, and the hotspot on the phone feels like it is up around the dimple. Certainly feels hotter than 105. Not so sure it is the battery causing a majority of the heat .... Still have a few days to return/exchange at best buy, so any advice is appreciated

No restarts due to heat yet. Have rebooted in safe mode, seems somewhat better after watching a 10 min youtube video... Can actually play fallout shelter in safe mode somehow, and the heat isn't as bad in safe mode as it is regularly. Temp stays around 100 F. Any way to see if it is an optimization issue without a factor reset and reinstall?