The LG G3 has a removable battery but I returned my device after one day of use and went back to my Note 2 until the Note 4 releases (both with removable batteries). The LG G3 is very laggy and requires you to change certain android options to stop the lag. Also, the phone started to heat up in my hand after 20 minutes of watching a video. The power button on the back was very hot. The screen is okay but I also had one dead pixel which did not help my opinion on this terrible laggy device.
Nova Launcher can cure most custom skin lag.
Under Nova's settings - Set it to FAST. Animation to Slide.
Go to your phone's settings under Developer's Option and make all three animations 0.5x.
This even helps for TouchWiz.
But it is probably better you went back to Samsung. Low SAR and hopefully lesser chances of cancer. Better to be safe than sorry. After hearing news my Stepdad has a brain tumor knowing he talks on his cell phone for hours with clients since the Wall Street/Zack Morris phone days, I say GO SAMSUNG!