e/os is not for every one, same as Android is not : )
e/os does an amazing job in terms of privacy.
I adopted e/os coming from Lineage. I have a different device rather than a Faiphone.
It’s expected for the connection (both LTE/wifi) when hide my ip is on.
It’s also expected to run into issues with certain apps on any degoogled os. Overall, I found e/os to be a bit more compatible on that matter since I do no use any specific apps.
Feel free to check this out for app compatibility
Regarding default browser, I like it. It’s light, simple, and works fine for me. As Jenn pointed, Brave browser is a good option.
About battery temp, try closing apps when not in use. Apps in background will take up memory and battery. (This goes for any device regardless of os)
Happy new year to all!