If you are 21 or over, you don't need a government issued permission slip (CCW permit) to carry openly or discreetly in Arizona except - you cannot enter a place that serves booze unless you have a CCW permit (any state's), carry discreetly ("concealed") and don't drink - and the business doesn't post a sign about "no firearms."
21 or over it doesn't matter how you carry on yourself or in a vehicle.
Arizona law makes no distinction between loaded and unloaded.
For 18-21, only open carry and the law is ARS 13-3102.B.3. For vehicle carry, look at ARS 13-3102.B.3(e).
The best FREE information on gun laws in Arizona is here. I recommend reading it.