My impression in the betas when fighting alongside strangers was that everyone gets his own stuff. At least in normal play. I never actively created a party, so that might be different. But even in D3 everyone got his own loot, so I assume it is the same.

You have your own loot. Drops are personal loot.

Yes, with the exception of the shards that drop in PvP zones.
I may be missing others, but that’s what I currently know about.