As to the controller.....read the directions ( and I'm not trying to be a jerk ). One setting won't be appropriate for all conditions, and having your trailer brakes lock up when you don't want them to isn't a good thing. Learn how to use it and adjust it whenever road conditions change. That needs to be something you don't have to think very much about.
Water.....I never drink the tank water. I will brush teeth with it, but that's about it aside from cooking with it (if I'm boiling it in the process). I take bottled water with me for drinking. It probably wouldn't hurt, but those tanks sit for quite a while even with sanitizing.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition