I haven’t played any Baldur’s Gate games before but I’ve heard so much about this game that I’m going to buy it.
However, before I start, I always wonder about this: some games allow you to unlock any weapon at some point in the game, and if you miss one in some quest you can always go back. If you accidentally sell one you can buy it back or forge a new one again, or have it respawn. If you want some other class you can switch later.
Other games are not like that, and if you screw up or aren’t aware of [full in the blank] then you can’t unlock something.
What’s the story with BG3? Do I need to be careful and plan before going on missions?
You can’t always come back. I would say most things give you 2-3 chances and the order doesn’t matter but certain decisions are a one time chance only and if you miss it, it’s gone. And if you miss those 2-3 chances, things are also gone for good.
For weapons the best example is during the “Prologue”. While you are still on the Nautiloid there is a strong enemy with a burning sword. If you play as “intended” and ignore the enemy, you won’t get it. And there is no option of getting it later (to my knowledge).
Then there are a lot of other decision where you aren’t sure of any long-term consequences. During the first 3-4 hours this bothered me and I did a lot of reloading trying to find the “optimal” way. But by now I embrace it. I finally have a solid idea behind how my character would act and just go with decisions inline with that. And I will have multiple play throughs of the game almost certainly.