I have the Att N9 and they modify the software so that it doesn’t have the same level of control over WiFi and Bluetooth settings as is found in other variants. But in my case, I found that some of the default settings under connections were causing higher system battery use. I’d suggest going into settings>connections>more connection settings and turn off nearby device scanning. Also, under WiFi tap advanced and turn off network notification. For me, I have all the options under WiFi advanced turned off. Those made a big difference for me. I also turned off always listening for Bixby and google assistant. I use them but don’t need them listening all the time and using battery.