You definitely can, Short Swords and Scimitars are both light, anyone can verify that with a level 1 character with 30 seconds of effort. Just saying.
meh it was rapier not scimitar
https://baldursgate3.wiki.fextralife.com/Sword+of+Screamsboth rapiers deals much more dmg then short swords
What was a rapier? You clearly stated that you cant duel wield Short Swords and Scimitars without the Duel Wielder feat.
You haven't a clue you obviously believed that you can only duel wield daggers without the feat, which is why you were making all your damage comparisons against daggers.
What does it matter that rapiers are D8 when there are no rapiers.
By the time you reach Last Light inn you have Sword of Screams and another +1 rapier. You will have to wait to Act 3 to get Harmonic Dueller +1 but the special is no good it uses charisma there will also be a +2 on a merchant as well in Act 3.
But at Last light you will have 2 pucker short swords both very rare +2s Knife of the Undermountain King and Sword of Life Stealing.
My point is that D8 weapon itemisation is poor and it is not worth going for Duel Wielder feat when D6 are what you are going to get. Even at end game the non light legendaries available to duel wield with are also D6 and to use them requires strength along with the feat. Or just forget the feat and strength and use light weapons there is a short sword legendary.
https://bg3.wiki/wiki/Weapons list all the weapons and some that should be in the game but are not.
