I ran Shadowheart, Gale and Asterion for the whole game, playing as Paladin myself. I find almost all companions to be somewhere from irritating to downright annoying and badly written, so I did it purely for their classes.

The game just disappeared off my home screen on ps5. It was there yesterday, hone today. Wtf..

Best advice is to rotate them. Some of them unlock unique dialogues in some parts of the game. If you really feel like benching someone, I think Karlach is your best choice. She has few utility outside combat and her story is most basic and with the least amount of unique dialogue/interactions 

Astarion is good for rogue utility, and Gale is great because he's your only Inteligence unit (unless your main character is also a Wizard). You can't go wrong with Laezel either, great fight unit and very important story overall

In act 2 keep Shadowheart in your party the most you can. She's almost the game deuteragonist in part 2

Depends of your Tav really 

My advice is to make your Tav a Charisma unit to help dialogue checks. Paladin, Bard, Warlock and Sorcerer are your best options  

If you don't have any charisma unit, consider keeping Wyll as he has high charisma 

Keep Astarion. He's not only hilarious but it's not dependent of spell slots meaning you almost never need to switch him because he's running out of energy. Plus Rogue and Stealth utility is simply great 

Edit: Looking like your Tav is already a Rogue. In this case bench Astarion

For martial units Karlach or Laezel. I think Laezel is better because of Warrior utility in combat 

Gale if you need a Caster. He's also good for Intelligence checks 

Healers are not really necessary. If you want one reclass Shadowheart as life domain cleric great for healing and good damage dealers too, her trickery domain absolutely sucks. If you want a caster go for Light domain, absolutely busted it's like a Wizard who uses Wisdom instead of Intelligence. If you want a caster who can do fine as martial unit War Domain and Tempest Domain are great, just remember to respec her to increase her Strength 

This of course considering you don't want to change the cannon class of anyone. If you respec keep the ones you like the most to fit any role 

The only annoying and badly written are the Minsc, since he's from the older games they couldn't change him, and Halsin who I don't even understand why is a companion since Jaheira joins you and it's just much better in both personality and story

Minsc and Jaheira are fan service for old fans, but done terribly.

For me Gale was least annoying, but they are all as if coming from some cringe worthy young adult fanfiction.

For all the system mechanics they are good at, Larian can't write for shit.

Oh stop, they can write. They can't world build well but some of the quest writing in Divinity OS is genius as well as the stories of the characters being brilliant. Can't speak on Karlach yet but they are binded by D&D, they can't go nuts with their own stories which I think may ve the downfall of this game in my eyes compared to Divinity OS2. 

Game is amazing, but yet again it wiped it's half downloaded self off my SSD. Wtf is the problem, can inly find one other with this issue and no resolve.

I'm thinking about playing the first one - the only CRPG I've played was Torchlight but I want to get more into the genre than that.

I'll play BG3 in the future, heard a lot of good things about it.

No, they really can't. Planescape Torment has great writing. KOTOR 2 has great writing. VtM: Bloodlines has great writing. Tyranny has great writing. Disco Elysium has great writing. Larian's stuff is way, way below that.

When it comes to companions, BG3 is also way, way below DA: Origins, which it tries to emulate in that regard.

Being tied by D&D has nothing to do with it - there's plenty of well written stuff for Forgotten Realms, BG3 is just not one of them.