While you'll be confronted with a lot of choices over the course of Baldur's Gate 3, there are a lot of fairly major ones in Act 1 of the game, likely due to the fact that the Act spent so long in early access. One of the major early decisions you'll make is whether to side with the Druid Grove or the Goblin Camp, and there are some hefty consequences to both choices.
Who should you side with in Act 1?
Siding with the Druid Grove will require you to basically wipe out the entirety of the Goblin Camp. However, once you're done you'll be able to get the Druid Halsin to join your camp, and Karlach will stay around. You'll also meet up with the Tieflings again later in the game and can continue to help them out. This also sets you up on the good path of Baldur's Gate 3, with recurring characters galore.
Siding with the Goblin Camp is very much painted as a bad decision. If you go forward with the Goblin Camp and invade the Grove then you completely wipe out all of the Druids and all of the Tieflings that are residing in the Grove. You also completely lose the ability to get the Druid Halsin in your camp, and Karlach will leave your party (if she's not already in your party then when you meet her she'll immediately be furious at you and you'll likely have to fight her). However, this is the only way to recruit Nightwarden Minthara to your side, and the only way to romance her. If you don't do this, then you'll be unable to get to know the cruel Drow.