I am not asking to make sneak attack twice. I am asking to chose if I want to use my sneak attack on my off-hand or my main-hand.
About only attacking with off-hand. Those are the 5e rules:
"When you take the Attack Action and Attack with a light melee weapon that you're holding in one hand, you can use a Bonus Action to Attack with a different light melee weapon that you're holding in the other hand. You don't add your ability modifier to the damage of the bonus Attack, unless that modifier is negative."
If you don't use your action to attack, you can't attack. It doesn't matter bonus action or not.
Good points. You are correct.
The Internet discussions made me believe you could use the offhand attack without first doing an attack Action, but your reading is the right one. My bad.
