One more question, again without giving direct spoilers, does any of those 8 companions' quest expand in the White March? Meaning is it worth saving any one of them in particular till I play a second time with the White March expansion?

I see Lore is mostly used in dialogues. Can I rely on Companions to use Lore in such situations, or is it something I must know myself?

OK, think I'll go with Aloth, Eder, Pellegina, Sagani and Grieving Mother with myself as Rogue. I'll keep the other 3 + 3 from expansion for my second White March run (will choose 5 of those 6).

Will this party work? Any 2 companions who don't like working together? Or 2 who are good to be with each other but I'm keeping apart? Or any skillset I'm missing or other form of trouble I'll get with this party?

I will play it on my second run. That's sad to hear. So if I want to finish all companion quests, I should do multiple runs?

I made that mistake as well. Not worth it. The game encourages you to shuffle around your party. XP isn't a problem.

Gotcha. So you do finish all companion quests, but instead of sticking to a party like BG, you'll be shuffling companions around?

Heh, I see you play RPGs the same way I do.
It recently ruined my Pathfinder playthrough when I learned I can't anymore get companion I picked before I started the game. I don't think it is worth playing without it but it's your choice. There are only 2 quests that need you to keep someone for prolonged time in your party (urance and Grieving Mother) so it si possible to finish all in one sitting. You will need to do a bit shffling, though, as most companion quests have several parts in various Acts and you would need to take them back several times to complete them all. If you are sure to paly it again, I find it better to not change the party that much.
It's up to you how you prefer to play. I played the game twice and first time I mostly stuck with 4 companions and tried several in the last spot and it worked fine and second time I did the shuffling and completed all companions quests but I certainly used some a lot more than others and I still had good time with it. From RP perspective it makes more sense to not use all of them but it really depends how you want to play it.
While some of them bicker a bit sometimes there are no companions that couldn't stay each other like in BG. There are some that get along with each other better and offer more banter but again, nothing to worry about too much. They are not necessary. Locks and traps are handeld by Mechanics skill and anyone can learn that.
They can be good damage dealers, though, and are very useful in fights. Must in what way? Story-wise or gameplay-wise?
I don't think any of them is but I think milage may differ. They do not. You can complete all quests withotu the expansions. Those companions have some new interactions with expansion stuff, but it doesn't directly affect their quests.

Yeah.
My very first BG game. It was one of my first RPGs, and definitely the first party RPG. So I read the classes in the manual, and man I can't decide, I want to try everything all weapons, spells and thieving skills. So I go with bard. I know he won't be as strong a figher or as good a spellcaster or thief as the respective classes, but still decent in all. Right?
After playing a bit I learned that:
A bard can't use all thief skills. Just the useless pickpocket.
A bard can't cast priest spells (yup, I thought he would. Note that I didn't even know that DnD existed before I opened the manual). Just mage spells. My 15 WIS is wasted
None of this really matters at all, because you get a party of 6 people, so you can try everything by getting a mixed party. And you get a bard NPC early on any way.

Man, that was a great game any way.

But since then, if I know you get NPCs, I plan my whole party in advance. I was thinking storywise. Like Imoen isn't necessary in BG2, but is a nice fit story-wise.

Thanks for all your answers. Thanks. Again I was thinking of Imoen getting new "quests" in ToB expansion.

OK, I'll go with Rogue (player) + Aloth, Eder, Durance, Pellegina, Sagani. By the time I reach Grieving Mother I'd have a good feel of the game, and I'll exchange on of them for her.
Probably will go with 4 core + 1 exchangable, but I'll play it by the ear and see how it looks once I get a hang of the game.

Man, so excited. I haven't played a decent party RPG since 10-12 years.

Heh. I think many people have similar stories with absolutely useless characters and one does sometimes remember them better and perhaps more fondly than regular well-made ones.
I don't even know what I played first time and I'd bet it was awful one. It didn't help played it with 2 cousins and we argued about everything we were to do. Pair it with any of us barely understanding anything in english and it was interesting playthrough. I don't think we ever managed to get into the city of Baldur's Gate back then.

It sure was. I have dozens RPGs to play and I caught myself recently pondering another playthrough of BG again because I found all sheet of papers with possible party compositions I created.

I don't think there are any. Quests of some of them provide deepr backstory to main quest (mainly Durance, but also Aloth and maybe Grieving Mother) but I have almost all of them compelling on its own and none of them crucial to have.

On the companions side this is 4/5 what I went with my first run and I think it worked quite well. I had Kana instead of Durance and didn't like him much gameplay-wise but I liked his character. I didn't like Durance as person as much but I think he has more interesting backstory.
Bear in mind that for his quest you have to talk with him from time to time, even if there is no indicator to do so.

I hope you enjoy it.