Cooking – think making a skillet dish, an omelet, baking stuffed bell peppers, that is using a recipe.
Baking – think dinner rolls, hamburger buns, breads, pastries, this is using a formula, and there is a difference between a recipe and a formula.
Stated often in the recipes I have listed here on this site is what I call variants, things you can to change up, optional items. And as I state many times, recipes are not set in stone and can be changed on the taste of the user or with what is available or on hand at the time.
Cooking, just volume measurements are adequate and perfectly fine.
Baking, one can get away with volume measurements, but the preferred method is by weight. Digital scales are very reasonable in cost and very accurate. If you have a pastry or bread formula in weight and volume, use the weight measurements if you have a digital scale.
With baking formulas, unless one is a very experienced baker, always follow the formula, reducing one ingredient may have serious affects on another ingredient, and these affects are never good and the end product you are making will not turn out well.
Information provided courtesy of good friend, Garland Davis, US Navy Cook (Ret).