I had my DS in 2012, and then it was and I do believe it still is recommended to make up the bottle with hot water, not boiling hot though. Because the formula is not sterile.
So you need the water to be hot so it can kill any germs/bacteria etc. in the formula. That is the reason for the hot water, it also mixes better and quicker/easier imo. The water doesn't have to be boiling hot, because that can also break down the nutrients in the formula.
Milk is good for 2 hours once you make it, and good for up to 1 hour once baby starts drinking from it. You can also pre-make them with hot water and store them in the back of your fridge for 24 hours.
For going out I would recommend you bring hot hot water in a thermos and make the bottle when needed in that moment. Fresh is best and is recommended, but obviously isn't the most practical for everyone. I would still highly recommend making it up with hot water.
Also there are on the go packets you could use, or the storage bottles in which each section you put enough in for 1 bottle and then you just 'pour' it in the bottle.
It also isn't recommended to warm up formula in the micro because 1. microwaves tend to warm up unevenly and you can risk getting hot spots. 2. microvaving water/pre-made formula can break down some of the nutrients inside.
Also never re-heat formula.
hope this helps! you don't have to do the things i've said, but i have done a lot of research and this has helped me. Even though it could sometimes be inconvenient (Imo).
Also having a prep machine is handy
though I've never had one before so I can't advice you on it.