I would suggest checking https://www.youtube.com/@DungeonDudes if you are about learning how to make the most out of it. The guys know the rules quite well and know how to build quite powerfull characters. Its more than you need for for BG3, but I feel like if you check their videos about feats and some adivces for multiclassing you should know what are considered to be power builds and then you can see for yourself how much you are willing to deviate from it.
Personally I think you won't need min-maxing as much as people claim it. If you have a specific playstyle you might get some odd combinations going that are still efficient. But if you want optimized builds there are a few well-known combos that you can find on that channel or probably here.
Biomag, thank you for that youtube link! I'm not really a D&D person, so it's really helpful to watch a podcast style of people talking about the different possibilities. I'm watching the ranger video right now.
Happy if it helps. I watched a lot of their content, I guess there are channels that are even more focused on min-maxing (treatmonk or something like this, will be mentioned in their videos and they worked together in a few). They also have a couple of things where they skew things based on their preferences - like allowing crossbow experts to use a weapon in the other hand and not affecting reloads or not using action economy for switching weapons - all of which affects a bit their view on things without them noticing and there are other things based on how they play on their table
But overall they are solid and definitely good enough of a source to get a good understanding while keeping in mind that your table (or video game) might have some differences that can affect some of the views significantly.
