Formula bottle question

Hey ladies,
So I've been using the liquid pre-mix formula for the most part because that's what we started with since we were mixing it with breastmilk for a while. I am traveling in a week though and I am thinking that the powder will be easier to travel with since it doesn't have to be kept cold and I don't have to carry around a bunch of pre-made bottles.
Just wondering what type of water you use to make bottles (bottled, boiled, tap, warm, cold)? What is easiest when you are on the go (airport, disney, etc.)?
Thanks!!

When I started using formula, I just used warm tap water.

When we travel or we're out and about, I use bottled. When we're at home, I use warm tap water.

With my daughter I used bottled water or boiled water and put it in a thermus and brought that so she could have warm milk but at home I just used warm tap water.