I think the power curve of the 2nd one really hits when you started off with your character in the first game killing rats in a basement.

As an aside I started Seige Of Dragonspear reecently because it was really cheap on Android and I was stuck on a long bus journey. I think it's actually pretty decent and potentially would be a good starting point if BG1 was too slow. So far the writing has been similar to the other two games albeit not quite on par. There is no tutorial on the mechanics or anything like that though.

Edit: One thing about BG1 is that it can be absolutely fucking brutal in an old school way. I was in Chapter 5 in the eponymous Baldurs Gate and a sidequest triggered where an NPC told me they had poisoned my entire party and I needed to follow them to an alleyway to get the cure. I assumed this was a ruse and my party was going to get mugged/jumped in the alley.

Fast-forward to 4 hours of gameplay later, 2 weeks of in-game time. I was on Chapter 7 on my way to confront Saverok and my entire party keeled over and died. Turned out they actually had been poisoned and none of my stacked saves went far enough back to go and complete the sidequest to avoid the poisoning. So I was totally soft-locked with no way to complete the game by conventional means.