I haven’t seen these styles in person, but they look fun if you’re after a pair of interesting denim bottoms. Shorter than regular jeans and longer than denim shorts. The tailored waist provides ample structure. Fab combined with a boxy cropped top, soft tucked top, welted sweater or untucked fitted knit top.
Remember that denim is stiff, which means that the silhouette will create a voluminous effect on the body. The wide styles in particular will feel like “a lot of culotte”. Styles with narrower side seams are less dramatic, but will create a more streamlined effect despite the rigidity of the denim. And yes, you can wear culottes with flats.
Petites can absolutely wear denim culottes, or any style of culotte for that matter, as long as the length is adjusted to create the right proportions for your height. Unless the styles come in a petite length, they will probably require shortening.