Please follow this guide below and see if it improves your experience. My guide is not directly meant for charging issues but some of the suggested settings could be connected to your issue and make it go way.
First of all, restart your device. It solves a lot of issues. Your phone will work better if you restart it once per week.
Second, go to system settings -> battery -> powermaster -> auto-start manager and prevent all the apps to auto start that you don't need a notification from.
After this go to system settings -> advanced -> Mobile Manager -> Memory cleaner -> Turn on Super Clean mode -> enter app list and uncheck any app that you must get notifications from -> go back -> open recent apps overview and press clear all.
Restart your phone.
Our Armoury Crate Game Profiles and X Mode is also a good way of improving performance.
Here's a Game Profiles guide for Call Of Duty Mobile that will help you understand the possibilities with X Mode. I hope it inspires you to find the best settings for your game and device. You will notice that the device is acting weird before that so you can exit the game and adjust if you've made any too extreme changes.
https://zentalk.asus.com/en/discussion/18439/game-profiles-guide-call-of-duty-mobile-armoury-crate-x...If none of the above tips help you to improve performance, then maybe the performance issue lays with the game. Export your armory crate settings, reinstall the game, restart your device, open Armoury Crate and import your games settings, start the game. Hopefully this will fix it!
A final note worth mentioning, playing with charger, means hotter device and cpu mitigation which might result in frame drop
