First person animations

I am making a multiplayer fps. What I want is to be able to see legs of my character when looking down (like in "The Forest") and seeing the animation of the other players. The game isn't about guns but only melee weapons. So I have a few question :

• Should I use the same animations in first person and in third person (for the other players) ?

• Should I use a character controller or a rigidbody ? (custom scripts)

• Can I have animations on the arms of my character regardless to the animation of his feet ? (such as moving backwards while attacking with an axe)

Thanks.