Unlimited Blade Works: The Guide to the Ultimate Paladin/Sorcerer Multiclass

[MajorDefunction]

Divine Smite is not a spell, so it cannot be Twinned (nor can any other metamagic be applied to it).

Fire Dragon Sorcerer would give your castings of Green Flame Blade extra oomf with its level 6 ability, which helps make up for the lack of Extra Attack, so I think that it's the most common choice. The other two published origins have abilities with interesting applications in melee, but they aren't as consistently helpful.

Alright, thanks!