As re: the battery - I am now having to keep it charging most of the time - have two cords for this; one, next to my recliner and one next to my bed. If I am streaming a movie, my charge drops rapidly, unless the tablet is plugged in.
I am sedentary due to health issues and my Surface 3 is my constant companion. There is probably something I could do to conserve power, but I don't understand what.
Anyway, the power management tab is on the file that one pulls up when one follows the procedure to locate the Realtk driver. There are two options under it - the first one being the one I am talking about.
Have not experienced many of the issues you mention - just the sound/video thing, an occasional problem with network adaptor settings and times when my cover keyboard has a hissy fit. This last is usually mended by giving the screen a good cleaning and
restarting.
Are you talking about in device manager? You didn't make yourself too clear. The first one I '' allow this computer to turn off this device to save power''. That is under the Power Management tab when you double click on Realtek 12S Audio Codec.