I wouldn’t consider maps to eat the battery per-say. The location services will use battery, but you can always close the map app when not in use. It won’t affect others being able to see your specific location. I use google maps directions to get to and from work and have location services on all day during normal use and generally get through a day on a single battery charge (Samsung Galaxy S6 Edge). However, we definitely use an external battery when in the Disney parks regardless between using the Lines app, MDE app and maps/camera/text.
Hangouts definitely doesn’t charge for the chat service. It’s just like email. My husband and I use it pretty interchangeably with text messaging. There is a separate app. I’m not quite sure where you are seeing the $0.00, but that is likely for the phone or video calls. Although we use hangouts to video chat with our family in Germany and I don’t believe we pay for it!