Should i mix formula with bottled water?

No: In most places tap water is safer than bottled water, especially in plastic bottles: http://www.Hhs.Gov/safety/bpa/ boiling will remove chlorine and kill microorganisms if any.

Yes: Clean, pure water from any source can be used to mix formula. Bottled water is fine. Tap water may be filtered to remove trace chemicals and possible microorganisms/spores, and then used to mix formula.

Depends: Most urban and suburban America has monitored high quality water supplies. They monitor for purity and add needed fluoride that may or may no be present in some bottles supplies. If you have any concerns about your own plumbing, bottled water may be a better choice.I would look into where it is sourced and what it contains .It may not be as well monitored as your city supply.