Regarding open world, I liked BG1 more than BG2.
Right from the start you could go everywhere except the city of Baldurs Gate and some quest related areas . . . if you survive. It was very easy to run into encounters that are much too hard for you.
I liked the original Divine Divinity and Gothic 1+2 too. You can go everywhere from the start, if you survive.
The only condition: There should be several options about what to do next for characters of any level.
In D:OS2 I have the problem that the power difference from one level to the next is so huge that you sometimes feel forced to do encounters in a specific order and you run into problems if you do not know the game so well that you have problems to find an encounter that fits your level.
One more reason to avoid the exponential number groth of D:OS2
I also liked BG1 more for the same reason. I think it's a difficult task to balance encounters with everything open from the start so I think some developers avoid it or break things into "Acts" to make it easier. I think it should be done where in the starting areas encounters are easier then as you get further from roads, cities, patrol areas encounters get harder. Maybe deeper in dungeons they get harder. I am really not a fan of having encounters always be survivable for the players. I am more old school where there may be some warnings that an area is particularly dangerous or have some NPC's talk about how bad or dangerous some areas are but let the players go where they want. It's what I do with a tabletop session; if my players ignore subtle hints about a dangerous area well some of them are going to be rolling up new characters.
When you gain a few levels and can go back to an area you felt was too dangerous you get a feeling of accomplishment and the "Acts" system kind of ruins that for me a bit where everything in Act I is level 1-10 (Or whatever it is). The world should be dangerous and not always be balanced (like 4E D&D kind of was)
