Does a multiclassed Hexblade warlock/paladin's Cha modifier stack with their Str or Dex modifier for attack rolls? Or does it replace Str/Dex mods?

Question

I'm creating a fun villainous figure for my campaign. The choice has fallen on a Paladin-Warlock hybrid. The general idea is to take 2 levels in Paladin for Divine Smite, and then pound 4-5 levels into Hexblade Warlock. Blade-summoning for the flavour, good at all distances, quite mobile, and pretty tanky due to allowed armour-class.

Since Hexblade warlock can use his Cha for attack rolls, will it stack with his Str or Dex modifier depending on the weapon? Or will I have to add my Cha mod instead of those stats?

Answer 1

You may choose to use Charisma instead of Strength or Dexterity

This is covered in the description of the Hexblade’s Hex Warrior feature (XGtE, p. 55-56):

Whenever you finish a long rest, you can touch one weapon that you are proficient with and that lacks the two-handed property. When you attack with that weapon, you can use your Charisma modifier, instead of Strength or Dexterity, for the attack and damage rolls.

It doesn't stack; you choose whether to use Charisma or the usual ability modifier - but not both - for attack and damage rolls with that weapon.

Answer 2

The Hexblade warlock's Hex Warrior feature reads (XGtE, p. 55-56):

When you attack with that weapon, you can use your Charisma modifier, instead of Strength or Dexterity, for the attack and damage rolls.

So you may add either your Charisma modifier to attack and damage rolls, or your Strength/Dexterity modifiers as appropriate, but not both.