If you have a tummy, the key is layering. Wear a looser top over the skirt, rather than tucked in. Then add a scarf or long pendant to elongate your body and draw attention. And a waistcoat or jacket if it’s cooler.
With a tummy, a plain skirt and tucked in top with no layering may leave the eye to settle on your tummy. Nothing wrong with that if you want to rock your curves, but not so good if you’re self-conscious.
A-line styles with a sturdy waistband are better silhouette than a sheer straight style, like your first example. Slightly above the knee more flattering if you have slim legs.
And always go for a slightly larger size, so it fits loose on waist and tummy. Skirts that are too tight on waist and tummy are unflattering and uncomfortable, unless you want to embrace your curves.