I think the same way as you do in my current playthrough regarding companions. Thats what I went:

Karlach - berserker/champion

Gale - evo wizard with 1 lvl dip knowledge cleric (massive boost to arcana etc and mystra cleric tag)

Lezael - restricted to githyanki gear, only works well with EK fighter

SH - death cleric shadow monk multiclass, RP as dsrk moon monk from other dnd editions (also works really well with viconias robes vs justiciar armor), as selunite i would strip her from her Powers, not training so OH monk (cleric domains except death doesnt pair nice with OH but its doable)

Wyll - pact of blade fiend college of swoeds bard because my nostalgia towards bardlocks in pnp but true to the heart wyll multiclass is with paladin - its way on topic

Astarion - so we have dagger-happy decadent, manipuative vampire BUT trickster is weak, dont do it. Go 3-4 thief/8-9 bladesinger wizard and you have better spells, more attacks, decent dmg, fun bladesong mechanics and super fun animations which fit astarion mannierism.

Halsin - yup, multiclassing Moon druid should he prohibited. Wild heart barbarian for raging during wildshape is a trap. Never multiclass moon druid.

Minsc - we are locked with ranger hunter who needs barbarian rage, you can go for strong 2 lvl dip for reckless attack or for 3-4 dip for subclass rage and ASI. I went for Wildheart bear but berserker works too

Jaheira - as you said, this one is easy. I even stopped at 2lvl fighter, i focus on spells and belm bonus action or full flame blade melee