My samsung has the feature built in, but on that old phone I rooted and installed Advanced Charge Controller. (Not feasible for most people i know)

My old phone with 3GB ram was hell (granted it had a weak SoC too). Now that I have 8GB (on a midrange phone too), it’s become much more enjoyable to use my phone. Everything is snappy, nothing ever freezes

Android 7 is quite old though, isn’t there any custom ROM development for your phone? I know there are downsides but it’s usually been fine for me

Not charging my old phone to 100%, rather to 85% or 90% has helped with battery longevity immensely. After almost 5 years in use, accubattery still shows 80% battery health, and even if that’s not accurate, it still lasts quite a while. The SD625 that phone had was very sluggish though, so in the end I still replaced it