A vinegar you understand is more useful than five you use nervously. Start with one whose flavor suits your food, such as a mild wine vinegar or rice vinegar, and notice how much changes a spoonful of dressing.
Seasoned rice vinegar may already contain sugar and salt. Balsamic vinegar can bring noticeable sweetness. These are not reasons to avoid them, but they explain why equal volumes do not always give the same result.
When a soup or bean dish tastes flat, test a few drops in a separate spoonful before changing the whole pan. Acid can sharpen flavor, but it cannot remove excess salt. Keep ordinary cooking advice separate from preserving: a vinegar substitution in shelf-stable pickles requires a tested preserving recipe with the correct acidity.