agree about neera

lilarcor has more depth and a better voice actor than dorn

The best / easiest is:

Main character: pure Kensai for attack speed, thac0 and damage bonus. Thac0 and attack damage bonus continue to increase into high levels, whereas they would not on a dual-class Kensai Mage character. You also don't have to worry about waiting for your character to become useful again, as he is not dual-classing.

Dorn: for tanking and dealing damage. Can wear an amazing helm: The Visage, and wield an amazing 2-handed sword: Ir'revrykal +5 which is almost as good as Carsomyr, bearing in mind that Dorn has much more strength than Keldorn without a Giant belt and Keldorn cannot acquire or wear The Visage. Dorn can also wield Soul Reaver. In the endgame, Dorn also has the capacity to dual-wield Blackrazor and The Answerer +4, rendering him unstoppable.

Rasaad: Amazing damage, Thac0 and AC and Magic Resistance, without having to do anything complicated to achieve it. Must wear at least a Girdle of Hill Giant Strength belt and make use of the Gauntlets of Crushing though. Downside? Cannot be hasted. Redeeming ability? Can Whirlwind.

Nalia: Used as a thief character in the beginning, simply to disarm traps and gain extra XP since nobody else can do it. Later on becomes a powerful enough mage. Not quite as powerful as Edwin, but powerful enough. Edwin can't disarm anything though, and XP is priceless.

Imoen: Your second mage. Either Nalia or Imoen can wield the Dak'kon's Zerth Blade +2 and a defensive blade in the off-hand such as Arbane's Sword of Agility +2. The other character can use the Staff of Magi. The important thing is to have access to another mage's arsenal of spells.

Aerie: A multiclass Cleric / Mage. Which other character / race can multiclass Cleric / Mage? None, so you have to choose her. Once she's at a high enough level she can cast every spell in the book. Both books. You can equip her with a sling + shield, e.g Sling of Everard +5 to "Slay" golems with and Shield of Harmony +2, or the Staff of Magi. Nalia and Imoen can't use shields, though, whereas Aerie can. Very weak Constitution on Aerie though.

The main character can, provided shs's a half-elf. Or if she's a gnome, provided you don't mind having to take the Illusionist kit (more spells/day, but you lose access to Vampiric Touch and Horrid Wilting).

Also, if you happen to find an NPC named Quayle and cheat him into your party (Control-Q cheat), he will actually be a Cleric/Illusionist. (He is a normally recruitable character in BG1; the developers did let him keep his class in BG2; don't know if his stats are the same.)

Note that, in the party you gave, Imoen will be in charge of finding and disarming traps, as well as opening locks. Before you get her, you can use Yoshimo as a substitute for that role (though he does not get spells), or you can try to use Nalia's inferior thief skills.

(Of course, this assumes that you aren't going to skip Spellhold with a glitch, but doing so is clearly not intended and will skip important parts of the story.)

If you choose your main character as the Cleric / Mage then you can't select Kensai, whereas Aerie can always be recruited. If your main character IS a Cleric / Mage. however, then you STILL have to choose Aerie.

We're assuming Control-Q cheats are lame and pointless, thus Quayle isn't allowed. I'm sure he is a nice character to have in the party though,

IMO It's better to recruit Jaheira before you rescue Imoen and get some nice XP and items from her questline & romance as well as have some nice Druid healing.

I wouldn't call cheats "lame and pointless"; sometimes it can be fun to use them, and even if you are mostly playing without cheats, it can be useful if you want to know what the stats of your summons are, for example. (You don't have to save after using a cheat; cheat the character into your party, check their stats, and then reload your save game.) Also, sometimes a cheat might be useful if you get into trouble, or find a certain part of the game to not be fun.

With that said, it's OK to assume cheats aren't allowed; it's not OK to call them "lame and pointless", as there are definitely reasons some players may want to use them.

Is it still worth it if you can't do the romance because the developers were heterosexist, or because you're not playing a suitable race?

I like to take Aerie and give her the Robe of Vecna so she can cast either Cleric or Mage spells rapidly. She’s a buffing and nuking machine. If you also give her the amulet that Aran Linvail gifts to you, she’s even faster at casting. Getting off a Heal spell quickly during battle can literally be a lifesaver. Want her to tank? She can buff herself like no other, and if you’ve set her up to dual wield, she can take the Flail of Ages and Defender of Easthaven (two of my faves) into melee, and attack 3x per round while boasting 20+ STR and DEX (DUHM + Holy Power + Haste).

Jaheira is great other than her base strength, but there are belts and gloves for that. Fighter/Druid makes a great tank - and an awesome mage or cleric disabler when she casts insect swarms at them.

I tend to go F/T for my PC, mostly because I love backstabbing. Plus once I get “Use Any Item”, I can then use Carsomyr, albeit not for backstabbing. I use Staff of Rhynn through SoA for that.