ONIONS. When onions are called for in a recipe, if it doesn’t specify the type, then use any type you like. However, when it does specify, then those recommended have been found to work the best in that recipe.
Sweet vs hot: When sweet onions are called for in a recipe, it refers to large Spanish yellow onions, Maui, Texas, Vidalia, Walla Walla, or others that taste comparably sweet. By using a hot or strong onion in a recipe that calls for sweet, you will be injecting too much onion flavor into that recipe.
However, many so-called sweet onions in the market these days are essentially hot, so when a sweet onion is called for it also refers to the texture and size, since sweet onions are larger than the small garden yellow variety, with thicker petals/layers and a broader bulb.