I was an iPhone user for several years and this is my first Android phone. How in the world do I change what apps run on startup, and how do I remove the apps that are already installed on my device that I don't want?
U cant uninstall the bloatware from att unless you root. But you can hide them.
As far as apps on startup. Many of those on startup are os items and shouldnt be messed with. Apple hides these things exactly for this purpose but android wants to give you the option. The only time you should be in these settings is when a rogue app is doing somethi g it shouldnt be like draining your battery.
This is an app that I downloaded myself though. I had to go in and force stop it but I don't know if there's a ways to set it so that it DOESN'T show up where my antivirus and WiFi (things that are constantly running) are in the drop down.