3rd part yes. Power Hungry, I dont think so. I was using a face with weather, fit, battery level, etc for a while when I switched to 2.0. I disabled (or at least I tried to) Google fit and lg health because I didn't need the constant heart rate monitoring going on. I got decent battery life. Then recently that all came back and it seems I can't stop it from turning on the green heart rate monitor and battery life is terrible now.
So... I switched back to a plain (no indicators) 3rd party face I used with 1.5 for a year with great battery life. It seems the heart rate monitoring isn't happening with that face but I'm getting terrible battery life on that too.
Lastly, for no reason, my screen is set to auto lock because I have Android pay. The watch no longer auto locks or asks for a passcode.