Pretty in-depth review after a first playthrough. It took him about 50 hours, but he played the early access, so he breezed through the first act, and he really knows his stuff. Normal people like you and me will probably need 70-80 hours for a playthrough. The game does have some issues, mostly minor bugs towards the end of the game, and the camera and inventory system can be a bit funky. However, with all that said, it seems to be a massive game in its genre. If you like CRPGs or consequence-heavy games, you should seriously consider this one. Plus, it's woke and makes chuds seethe.
Is this a separate story? Or should I at least watch story overviews of the first two
It plays in the same world 150 years after Baldurs Gate 2. There are some characters from the first 2 games that appear in it and the city "Baldurs Gate" appears again in it. The game is made in such a way that you can go in blind without any previous knowledge. If you want you could watch a sort summary of the first 2 games I assume. I did stay mostly in the dark about Baldurs Gate 3 (so I dont spoil myself). Others might be able to say more on this topic.
Same channel has a short 12min story recap which I did watch. I think it goes over the most relevant story beats of game 1+2 but I never played them https://youtu.be/__GI7CrYnj8