Are items with +0AC are only aesthetic or do they bring some defense or other benefits?
They are just cosmetic.
It's common for new characters in RPGs like these to start out with basic clothing, which doesn't have any real effect in the game besides looks.
Any stats on the item will be displayed (as long as the item is identified). So, if you want to save a bit of weight and don't mnid oyur characters running around naked, sure, you can throw it away.
Keep in mind though, especially wizards won't get items with stats very quickly, as they don't wear normal armor, only magical robes.