Dual-wielding : the weapons must have the tag Light as per 5e rules. This is typically daggers, hatchets, shortswords, etc.
- Once in your hands, you can freely choose to make a single attack (Action) or use both (+Bonus Action).
Good news is the game uses the best of your Str or Dex if it is a Finesse weapon (most Light are Finesse).
As for using a versatile weapon in one hand, for duelist, it is just an oversight I presume and will probably be added later during the year.
