In the table top it specifically forbids any weapon with the heavy or two handed category.
Acording to Fextralife ... it dont in BG-3.
They get to use dex to their monk weapons for attack and damage, if they can do that for a two hander it could be very unbalanced.
Im affraid so.
Also I always assumed that the extra attack they get is an offhand punch? Not the level 5 one, the extra martial arts one.
Its unarmed attack ... it can be kick, headbutt, or something simmilar, not just offhand punch.

But they also get extra attack on level 5!
Meaning 3 attacks per turn at level 5 ... just as Berserker Barbarian (they are slightly stronger tho) ... or Martial class with Polearm mastery ...
4 if you invest Ki.
5 if you multiclass with Thief, or find some item that gives you additional Bonus Action, or with Haste/potion.
If im not misstaken.
Nah, I hope the rules prohibit any weapon and the dex to damage and attack only works with specific monk weapons and not just proficiency
I kinda do aswell.