Question about recipe ingredient.

[ProfessorGAC]

6. That Would Work

The acetic acid in vinegar is slightly stronger than the citric acid in lemons, but at a lower molecular weight, dissociated into the water a bit more easily. (Citric is 50% soluble in water; acetic is infinitely miscible)
But, the carboxylic esters in vinegar are more plenitful, which adds another floral fragrance & taste that citric acid can't.
It all boils down to a taste preference.
I'm big on using vinegar to offset both heat & sweet. But, that's a matter of taste.