1. I would like to play 3 player coop. Will it be reasonable to just play this as 3 player without the need of a 4th? Or can AI play a 4th player, I really doubt the last, but I ask anyway.
You can play with a party of three but it will be hard (in classic mode). If you want to play with a party of four the host will control two characters, one created during character creation and a companion the host gathered along the way.
2. Are the maps any larger? To me a bigger map would give a bit more sense of world adventure.
Not really, DOS2 is still a hub-based game. So the one map in the EA version is comparable to the map of Cyseal.
4. Any improvements to Inventory Management? Overall UI?
Yes, but please see the respective threads and information Larian handed out.
