Xiaomi backup is pretty good, restores all my calls, texts, pics, layout, icon theme etc.
(I dunno why anyone would need to back up WhatsApp daily!)
Factory Reset is underrated, everyone loves their phone when new, the software is a reason why. Xiaomi has it in Settings under Backup I think. I was gonna recommend clear cache but that involves going into a recovery layer and frankly if your backup is sorted you've got nothing to lose from a Factory Reset. You can do it then immediately update to latest software
There's further options. You might wanna Google Developer Options for your phone. On Xiaomis with MIUI you find the MIUI version number in settings > About Phone and tap seven times.
There's options in here to change (enable) the WiFi scan throttling and stop it "Always using mobile data" on WiFi. Those being switched off on your blower already might make these steps irrelevant but there's also more advanced logging to help figure this out.
Turn off MIUI Optimization - you'll thank me later
But yeah, if you notice it after a factory reset - unlikely, but we should do some stats digging. Wouldn't mind a screenshot of your battery usage stats - you should be able to see the biggest drains by Ranking. Screen should be top, no exceptions. For me, both the System and Google Services are under 2% - your milage may vary but something is eating that power
There are an absolute ton of options from this point though let's park it for now..
https://forum.xda-developers.com/t/improving-battery-life-on-miui-12.4139913/