1st choice - wear nothing if the dress shows your complete body contour and is real body hugging. I do it all the time, it just need a little getting use to. When i go for workout, i just wear my spandex or lycra tights straight up too, cant stand the sight of vpl through tights.   hope my comment helps. Cheers

A good pair of spandex tights will have a liner / longer gusset to prevent the center line of the camel toe from being imprinted through your tights, unless you want to get some from pasar malam or such. Whether or not you wear or not wearing a panty under your tights, the triangle shape will definitely be obvious, the difference is whether the line is visible or not. That is the only difference.