I like to set the refresh rate to 120hz, sharpening to 2, autofocus accuracy to 16, and leave the resolution at the default 1.35. It does drain the battery pretty fast, though, so you might want to lower some of the settings if you want to increase battery life.
Resolution, autofocus accuracy, and refresh rate are all saved globally. If you want to change the default sharpness value, click on the button labeled "Image" above the sharpness setting, then click on the save icon for the first preset. That'll load your current "Image" settings as the default for new videos. You can do this for each subgroup of video settings.
