With crap entry-level Android phones, you could just play music or use navigation in the background while you run it off a charger and it'll never go above 2% even while it's plugged in :)
I remember when Pokemon Go was the rage, a friends OnePlus would need to be plugged in to a battery bank the entire time, even then it still drained slowly.
That's a fault of the charger you're using, the phone has nothing to do with it.
No, it's not. It's a Qualcomm QuickCharge 3.0 capable charger that exceeds all charge requirements and has no problem with other devices.
Then maybe I misunderstood what you mean by entry level. Or maybe you own a model that is an exception. I deal with cheap (sub $200) chinese android phones a lot because we do development in React Native but it still has to run smoothly on these things, and I've never encountered these issues with phones newer than 2015.