The world is open world.
Difference between Jobs and classes? If youre talking about professions. Discipline of war and magic are battle classes while Land and hand are crafting classes.
Unique thing about crafting is that they all kinda intertwine with each other. And as well as you can be every class on one character just by switching your weapon. Spear for lancer then you can equip a staff to become a conjurer. And your jobs each have an individual level. Like you level up lancer to 10 then switch to conjurer you are back at lv1 conjurer... switch back to spear youre back at lv10 lancer.
I think loot is round robin.
And honestly the experience youre gunna have to decide yourself.